Checking SRIM 3.5 MeV 7Li is stopped in 9.06um mylar or 10.09 um CH2.

After the long run at 3.0MeV on 22/02/2018 we decided to put the 12um mylar back in front of the S2 and start tuning the beam for 3.45MeV 7Li. We also decided to tune the beam to a higher current of ~ 100pA to try and improve the detection rates.

At 20:54 The turbos were switched off. The manual gate valve for Ecodry 2, automatic gate valve for Ecodry 1, and line valves were closed.

Whilst the turbos spun down we removed the S2 preamp box from the top of the chamber.

At 21:31 the vent valve at FC-O was opened. At 21:49 we noticed the chamber was vented.

The S2 was removed from the chamber and 12um mylar mounted in front of it. The S2 was remounted in the downstream section of the chamber.

At 22:03 the manual gate valve was cracked open -> we began roughing the chamber with Ecodry 2. At 22:18 the manual gate valve was fully opened and we then opened the T1600 Backing valve allowing Ecodry 1 to pump the chamber. We then started the turbos.

During pump down the S2 preamp box was remounted on top of the downstream chamber lid. The lid to the preamp box was also mounted. The following pin diode preamp cables were reconnected: -15V, +15V, +ve test, input from lemo feedthrough, and HV.

By 22:34 the pressures in the chamber were CHUP = 1.3e-5mBar, and CHDW = 3.2e-5mBar. The S2 was biased to -130.3V, leak I = 1.54uA. The diode was biased to -70.1V, leak I = 0.00uA. The preamp power was switched on, correct currents were being drawn.

The target ladder was set to position 2, 80.024mm, no target or frame.

After tuning with no target, the GSSI slits were fully open at:

Up = 0mm

Down = 5.5mm

Right = 1.5mm

Left = 5.5mm

We found the following currents:

FC-4 = 740pA (upstream from bending magnet)

FC-0 = 430 pA (upstream from chamber)

FC-E1 = 70pA (downstream from chamber and GSSI magnet)

The target ladder was moved to position I, 95.010mm, blank 3mm frame.

After further beam tuning we obtain currents:

FC-E0 = 330pA

FCE1 ~ 200pA

Transmission: ~63%

At 23:33 CHUP = 6.5e-6mBar, and CHDW = 1.7e-5mBar. S2 bias = -130.3V and leak I = 1.66uA. Diode bias = -70.1V and leak I = 0.00uA.

We decided to call it a day. Both the S2 and diode was switched off for the night. The accelerator beam voltage ~ 1.4730MV.

Raffaele let a note for Liz to improve the transmission to 70% the next morning (23rd).

See next eLog entry #19 to continue the beam tuning adventure.

Yesterday (21st) night we saw this low channel, high rate (1500Hz) noise on the diode spectrum - see eLog entry #15.

This morning the S2 bias was ramped to -130.3V, leak I = 1.43uA. Diode bias ramped to -70.0V, leak I = 0.01uA.

Starting the DAQ with no beam, the trigger rate is ~250 Hz, with most triggers coming from the diode. Inspecting with the oscilloscope we find a very high noise of ~300mV. The amplifier course gain = 1K.

Lowering the course gain to 200 we decided to try sending beam on target VII and check the diode output on the oscilloscope. I was able to see some signals at ~3V, with very low rate ~0.1Hz

I checked the rutherford scattering rate using the Nuclear_Reaction-master.xlsx excel file, sheet "Rutherford Scattering" columns BH and BP. See attached.

With the current collimator radius = 0.5mm, at our scattering angle 152 degrees, we find an expected rate 2.72e-3 particles per second.

We decided to remove the diode collimator, for the 10X10mm diode this would give an expected rate 0.272 particles per second. This is still not ideal, and before the next shifts we should optimise the position of the diode to improve the rates. This is for a beam current ~40pA, so we would benefit from higher beam current too. A rate of 5 - 10 particles per second would be nice. For now we stuck with the current situation.

At 10:52 the S2 and diode biases were switched off. The preamp power was also switched off. The turbos were also switched off. By 11:48 I saw the turbos had stopped spinning and started venting the chamber.

Once the chamber was vented we managed to remove the central lid without needing to remove the S2 preamp box on the downstream lid.

The 1mm diameter collimator was removed from the diode, this completely destroyed the 0.9um mylar in the process. Next shifts we will use a metal plate to glue the mylar in place, avoiding this issue. For now we left no mylar in front of the diode, because this will not be useful until running 7Be beam.

We also decided to remount the alpha source, allowing us to check the diode is functioning as expected. The target ladder configuration is as follows:

After removing the diode collimator the central lid was remounted and at 12:50 the roughing pumps started. At 13:12 the turbos were started.

By 13:53 the pressures read CHUP = 1.2e-5mBar and CHDW = 3.3e-5mBar.

We switched on the preamp power. The S2 bias was ramped to V = -130.3V, leak I = 1.25uA. The diode bias was ramped to -70.0V, leak I = 0.01uA.

The target ladder was moved to position 7 (5.019mm), centering the alpha source in the beam axis and pointing upstream.

We were able to see the two highest intensity alpha peaks in the pin diode spectrum (ADC6 CH31) - so the diode is certainly working

At 14:06 we started an alpha calibration run for the pin diode.We collected data for a preset time 900 seconds. The trigger rate ~80Hz, Event Mult. = 3.0, dead time = 0%.

The save name is: /Remote_Objs/RData_1/180222141134

See attachment PinDiode_AlphaSpectra.jpg for a sample spectrum

The Ortec 871 Amplifier Settings were:

Fine gain = Max

Course gain = 50

Shaping time = 0.5us

BLR Auto On

The Delay Amp 1457 settings were:

Delay: 1us

Range: 10V

Polarity: Pos

At 14:21 the DAQ stopped, # good events = 61406.

Now we were ready to proceed with a beam measurement.

The target ladder was moved to position 3, 65.000mm, target: CH2 930ug/cm2 VII

We still see some alphas from the source, these are 5.1->5.5MeV, and from the kinematics we expect the beam scatters to be ~2.9MeV so there should be no overlap in energy.

I disconnected the pulser from the pin diode (it was set to too high an amplitude to appear on the alpha spectrum) and switched it ON for the S2 front strips. The pulser rate was changed from 10Hz to 2Hz. (Set to 10Hz when diagnosing pin diode)

With no beam trigger rate ~85Hz, event mult. ~ 8.0

We checked the beam at FC-E0, just upstream from chamber, = 45pA

We bombarded CH2 VII with 3.0MeV 7Li beam, trigger rate ~700Hz.

The pin diode rate for backscattered beam was very low, but we do see some counts at channel ~1300, which is expected.

We decided to run for 1 hour and see the rates.

15:00 DAQ started for 3.0MeV 7Li on CH2 930 ug/cm2 target VII

Save file: Remote_Objs/RData_1/180222150540

Trigger rate ~ 550Hz, Event Mult. ~ 6.2, dead time ~4%

Note: from previous tuning and running yesterday (21st) I estimate beam has already bombarded target VII for ~3 hours before starting this run.

At run time = 01:01:09 we have the following areas:

ADC 6 CH31 (pin diode) area between channels 1159->1268 = 285

ADC 4 CH24 (S2 back strip) total area = 7353

ADC 2 CH 3 (front S2 strip) total area = 21647 (2Hz pulser connected)

Ratio of back strip to diode = 76.0

We decided to collect data until 20:00 giving us ~5 hours of data at 3.0MeV.

At DAQ runtime = 03:03:09 we have the following areas:

ADC 6 CH31 (pin diode) area between channels 1159->1268 = 911

ADC 4 CH24 (S2 back strip) total area = 66704

ADC 2 CH 3 (front S2 strip) total area = 22335 (2Hz pulser connected)

ADC 2 CH 7 (front S2 strip) total area = 22734 (2Hz pulser connected) - more statistics than ADC2 channel 3, continued monitoring this channel instead of channel 3

Ratio of back strip to diode = 73.2

Ratio of last ~2 hours runtime = 71.0, so target is degrading

At 19:25 we decided to go to dinner and leave the setup to collect data.

At this time CHUP = 5.4e-6mBar, CHDW = 1.4e-5mBar. S2 bias = -130.3V, leak I = 1.71uA. Diode bias = -70.1V, leak I = 0.00uA.

At 20:50 we returned from dinner. The DAQ was manually stopped.

DAQ monitor:

Run time = 05:49:09

Event mult. = 6.2

Dead time =7%

# good events = 34296773

At the end of data collection the areas are:

ADC 6 CH31 (pin diode) area between channels 1159->1268 = 1847

ADC 4 CH24 (S2 back strip) total area = 124876

ADC 2 CH 7 (front S2 strip) total area = 43334 (2Hz pulser connected)

Ratio of back strip to diode = 67.6

Ratio of last ~ 3hours = 62.1 - so target is still degrading

The S2 bias = -130.3V, leak I = 1.75uA. S2 Bias ramped OFF

The diode bias = -70.1V, leak I = 0.00uA. Diode bias ramped OFF

Preamp power OFF

At 20:53 the pressures read:

TPU1 = 2.5e-6mBar

TPU2 = 6.4e-7mBar

TPD1 = 1.6e-6mBar

TPD2 = 1.6e-6mBar

CHUP = 5.2e-6mBar

CHDW = 1.3e-5mBar

See attached 180222_diode.jpg for the final diode spectrum.

See attached 180222_ADC4CH24.jpg for the final S2 back strip spectrum

See attached 180222_ADC2CH7.jpg for the final S2 front strip spectrum

DAQ Settings for ADC6 settings attached. ADC 6 has been used for the pin diode during the week starting 19/02/2018

On 21/02/2018 after beam tuning and pumping down at 18:07 the pressures read Up = 1.2e-5mBar, Down = 3.2e-5mBar. We were happy to power the detectors and try to observe spectra from beam in both the S2 and pin diode.

Whilst waiting for the turbos to spin up the Pin diode was daisy chained with the +ve pulser, +15V, and -15V preamp power cables used with EDI Preamp 2 for the S2.

Channel 3 of the Silena Quad Power Supply was set to -70V ready for the diode.

The S2 bias was ramped to -130.3V, leak current = 1.19uA. The Pin diode bias was ramped to -70V, leak current = 0.01uA.

The preamp power was switched on, +15V read current 0.8A, -15V read current 0.4A, as expected.

The pin diode output was split between an Ortec 571 Amplifier and channel 2 of a Quad TFA.

The unipolar output of the Ortec 571 Amplifier was sent to a Delay Amp 1457. The Delay Amp output was sent to ADC 6 Channel 31.

The Quad TFA output was sent to channel 4 of a Quad CFD. The CFD output was sent to the Lecroy 622 module and setup as an OR with the S2 strips. This OR is sent to the DAQ trigger.

We mounted the preamp box cover. The grounding cable for the ribbon signal cables was attached to the box. We confirmed the grounding of these ribbon cables with a voltmeter.

Now with no beam the DAQ trigger rate ~ 60Hz. This suggests the ~6kHz rate seen before is noise from the previously exposed preamp, note the downstream turbo is very close (a couple centimeters) to this preamp.

To double check the tuning was still ok we sent the 7Li beam to FC-0 = 48pA.

We decided to close the GSI slits located before the quadrupole and slowly open these to their values in eLog entry #14. We closing the left and right slits had no effect on reducing beam current, so we kept these positioned at 5.5mm and 1.5mm respectively. The up slit was already 0.0mm.

Slowly opening the down slit we saw the following:

We saw on the backscattered diode counts at channels 50 -> 400, even when increasing the Ortec 571 Amplifier gain to 1K and the fine gain to maximum.

We checked the faraday cup upstream from the bending magnet, FC-4 = 100pA.

We also checked the faraday cup just upstream from the chamber, FC-0 = 53 pA.

The Ortec 571 Amplifier settings (for pin diode) were:

Fine gain = Max

Course gain = 1K

Shaping time = 0.5us

Input = Neg

BLR AUTO ON

Uni Output taken with Out setting

The Ortec 935 Quad CFD CH4 threshold was = 175mV

At 20:50 we sent 3.0 MeV of 7Li beam onto CH2 930ug/cm2 Target VII. We started the DAQ whilst writing to disk.

The DAQ dead time ~ 3%, Trigger rate ~ 1500 Hz, Event Mult. = 6.2.

The save path and name: /Remote_Objs/RData_1/180221205456

It became apparent within the first 1/2 hour that the trigger rate (1500 Hz) is almost entirely from the pin diode.

At 22:10 we stopped the DAQ data collection, run time = 01:19:46, dead time = 4%, # of Good Events = 7180956.

We checked the current on FC-0 = 53 pA.

The beam voltage ~1.2730 MV.

Checking the detectors: The pin diode voltage = -70V, leak I = 0.00uA. The S2 bias = -130.3V, leak I = 1.46uA. Both detectors were switched off for the night.

At 22:18 the pressures in the chamber are:

TPU1 = 3.4e-6mBar

TPU2 = 7.5e-7mBar

TPD1 = 1.5e-6mBar

TPD2 = 1.8e-6mBar

CHUP = 6.1e-6mBar (also referred to as Up)

CHDW = 1.6e-5mBar (also referred to as Down)

See attached "180221_PinDiode.png" for the pin diode spectrum after the run. In the morning of 22/02/2018 we realised this was just amplified noise.

See attached "180221_S2BackStrip_ADC4CH24.png" for a sample spectrum of one of the S2 back strips

See attached "180221_S2BackStrip_ADC2CH7.png" for a sample spectrum of one of the S2 front strips

On 21/02/2018 we reattempted the beam tuning. We expected this to be easier now the rogue mylar is removed from the beamline.

At 8:30 we started the roughing pumps. At 8:37 the turbos were switched on. By 8:55 the preassures read: Up = 1.6e-5, and Down = 4.3e-5 mBar.

The preamp box was mounted on top of the chamber ready, the box lid was still left off.

The S2 was biased to -130.3V, leak current = 1.03 uA.

On FAIR DAQ with no beam: Trigger Rate ~ 8000/s, Event Mult = 5.0

The 10mm blank frame was in the beam axis. We began beam tuning. By 11:30 we had beam on the downstream faraday cup FC-E1 = 40pA, so now we can pass beam through the chamber - good!

We moved the target ladder to 95.010mm, swapping from the blank 10mm frame to the blank 3mm frame to assist in beam tuning. Now FC-E1 ~ 8pA.

We decided to move back to the 10mm frame to optimise tuning. The target ladder was moved back to position 80.024mm for this purpose.

We moved the slits located upstream from the bending magnet (close to FC-4) to 1.5X1.5mm.

We moved the GSI slits located before the quadrupole to optimise current on FC-0, the upstream faraday cup. We find the following slit positions:

Up = 0mm, Right = 1.5mm, Down = 5.5mm, Left = 5.5mm.

We also performed further tuning by adjusting the quadrupoles located at the immediate end of the tandem accelerator - note the beam tuning is very sensitive here.

After beam tuning we had the following currents:

For 10mm blank frame in beam axis: FC0 = 42pA, FCE1 = 30pA, transmission ~ 71%

For 3mm blank frame in beam axis: FC0 = 41pA, FCE1 = 13pA, transmission ~ 32%

We decided this was acceptable for testing

At 13:30 we switched off the S2 and vented the chamber.

After venting we did the following:

• Removed 12um mylar from the front of the S2
• Visually inspected the ribbon cable connections on the S2 connector and the vacuum feedthrough connector. I saw no loose connection and left the cable alone.
• Set the Si diode angle to 62 degrees relative to the beam axis (28 degrees relative to the normal of the beam axis) - in future we need a fixed angle mount to ensure this angle is reproducible
• Mounted targets on the ladder at the following positions:

The target ladder was set to position 3, looking from above I confirmed it was in the center of the beam axis.

The alpha source was removed as someone pointed out the ladder may be moved in such a way that beam hits the source. However later on (morning of 22/02/2018) I was informed this is being over cautious and we can leave the source at the far position 7 of the ladder during beam.

The ladder, downstream, and upstream lids were remounted on the chamber. The S2 (no mylar) was still on the downstream lid. The diode was still on the central lid.

The roughing pumps were switched on. However the following mistake was made: when both Ecodry 1 and Ecodry 2 were switched on, the automatic gate valve for Ecodry 1 was still open. This meant the chamber was evacuated at a fast rate, likely > 10mBar/s. When I noticed this after a few seconds of pumping the pressures read 10^-1mBar at the chamber upstream and downstream positions.

Speaking to David I learned Ecodry 1 may be switched on ready as long as the gate valve "T1600 Backing" is closed

Learning point: Ensure the automatic gate valve "T1600 Backing" is closed before pumping. This way we can control the roughing speed using the manual gate valve on Ecodry 2.

I wanted to inspect if anything was damaged in the chamber by this fast pump speed. The pumps were stopped and the chamber vented.

Upon visual inspection the S2 and 0.9um mylar in front of the diode were undamaged.

Target CH2 I on the ladder was loose at one side, the target ladder was removed and CH2 I at position 3 was replaced with CH2 VII.

Now the target ladder is in the following configuration: See attached IMG_2738.jpg

At 16:45 the roughing pumps were switched on, this time with the "T1600 Backing" gate valve closed. The manual valve was cracked open.

By 17:01 the pressures read Up = 4.2e-1 mBar, Down = 4.1e-1 mBar.

At 17:08 the turbos were switched on.

At 18:07 the pressures read Up = 1.2e-5mBar, Down = 3.2e-5mBar.

We are ready to connect the preamp box for the S2, and also connect the preamp for the pin diode.

The PB-5 Pulse Generator settings are as follows:

Fall Time = 100us

Rate = 2.00Hz

Delay = 250ns

Ampl = 0.50000V

Pol = POS

Pulse Top = Tail

Atten = 1X

PB-5 Pulse = ON

CLAMP = OFF

During the second beam tuning on 20/02/2018 we performed two pulser walkthroughs to determine the ADC offset.

For the walkthrough the rate was increased to 10Hz.

The first pulser walkthough was saved as: Remote_Objs/RData_1/180220170900

The pulser amplitudes used were: 0.1, 0.2, 0.3, 0.4, and 0.5 V

After this walkthrough I remembered channels 24 -> 31 of ADC 2 were unplugged from the RAL shaping amplifier, and so plugged these back in. I then repeated the walkthrough.

The second pulser walkthrough was saved as: Remote_Objs/RData_1/180220172838

Like the first walkthrough, the pulser ampltudes were 0.1, 0.2, 0.3, 0.4, and 0.5 V.

A sample pulser walkthough spectrum is attached.

The pumps were left on overnight, in the morning at 8:25 the pressure reads:

Up = 1.5e-5 mBar and Down = 4.0e-5 mBar.

We made a first attempt at collecting an alpha spectrum for the far S2 detector using ADC 2 and ADC 3. However ADC 3 appeared to be acting as a TDC for no obvious reason.

During this attempt we noticed ADC 2 channels 0, 1, and 5 had a high rate, and ADC 2 channel 8 had a low rate.

We moved the ribbon inputs on ADC 3 to ADC 4, the spectra on ADC 4 looked better. ADC 4 Channel 30 had a low rate.

We noticed ADC 3 was still active -> removing the ribbon inputs had no effect on the module writing to the DAQ. We raised the lower threshold of ADC 3 to 2046 (total 2047 channels), effectively stopping it from writing.

The thresholds for ADC 2 and ADC 4 were set to channel 40 for both. The thresholds on the RAL shaping amplifiers are set to 15mV.

At 9:09 we started collecting an alpha spectrum for a preset time of 900 seconds, finishing at 9:24. The dead time was 24% and the event multiplicity 3.2 (event mult. was 40 before removing ADC 3). The trigger rate was ~9kHz. The data were saved in /RemoteObjs/RData_1/180220091352/

To try and lower the trigger rate I removed the 6th breaker in the top IDC convertor box, which corresponds to the 5th channel of RAL I, which in turn corresponds to the 5th channel of ADC 2.

The trigger rate had risen (strangely) to ~12kHz, we saw ADC2 CH 0 had a high rate.So I removed the 1st breaker in the top convertor box, which corresponds to the 0th channel of RAL I, which in turn corresponds to the 0th channel of ADC 2.

Now the trigger rate was ~9kHz, with a good event rate ~ 40 Hz. We agreed that since the preamp box does not have its cover on there will be noise, particularly from the turbo located immediately downstream from the preamp box.

At 11:30 we started trying to tune the beam. Before sending beam I moved the target ladder to position 95.010mm, achieved by first moving the actuator to position 96mm and then back in position to account for backlash.

Note: All the target ladder calibration points were obtained by moving the ladder towards the actuator.

By 12:44 we were still tuning. We obtained a beam current of 200pA in FC-0, the faraday cup located ~1m upstream from the chamber, however we were unable to find the beam downstream from the chamber.

We were using the 3mm diameter blank frame for beam tuning, and decided to now attempt tuning with the 10mm blank frame.

We were using the only blank 10mm target frame available to support the alpha source, so we decided to vent the chamber and move this to an accesible part of the target ladder for beam. This would also allow us to inspect the beamline and check it is clear of obstruction with the telescope.

We switched off the detector and vented the chamber. I then removed the target ladder and switched the 10mm blank frame holding the alpha source with a 3mm blank frame. The 10mmblank frame was attached at position 2 of the ladder.

See attached (IMG_2709.jpg) for the first target ladder setup. See attached (IMG_2712.jpg) for the new target ladder setup.

We set the target ladder to 80.024mm for the 10mm blank frame, and then using the telescope confirmed it was in the beam axis. This involved removing the upstream lid and putting a piece of white paper in.

We then sealed the chamber and at 14:40 started the roughing pumps. The gate valve was cracked open -> we want a pumping speed <10mBar/s to avoid damaging the detectors and/or mylar foils.

At 15:04 the gate valve was fully opened and the turbos started. By 15:12 the pressures read: Up = 9.2e-5mBar, and Down = 1.0e-4mBar. The detector was biased at -130.3V with a leakage current 1.19uA.

With no beam the DAQ trigger rate ~ 6kHz.

At 15:29 we started the beam tuning with the 10mm blank frame in the beam axis.

During tuning the power supply on the 1st analysing magnet, located between the cathode source and accelerator, showed problems and was replaced.

At 17:50 I checked the S2 leakage current = 1.28 uA. The slight rise from 1.19 uA could be due to temperature fluctuations (8 degrees temp increase causes factor 2 difference)

At 18:20 we decided to vent the chamber and shine a light upstrean from the faraday cup FC-0. After switching off the detector and venting the chamber we discovered the piece of paper used to check the 10mm aperture alignment was left inside the upstream section of the chamber since the last time we vented. No beamspot was seen on the paper.

At 19:00 we restarted the roughing pump and cracked open the gate valve. At 19:03 the turbos were started. At 19:06 the pressures read Up = 7.0e-5, Down = 1.3e-4 mBar. The S2 was biased back to -130.3V, leak current = 1.20 uA.

We went back to tuning (third time today). With no beam we had a DAQ trigger rate ~ 2.6kHz, event multiplicity = 10.

We were able to see beam on FC-0, but unable to see beam on either of two faraday cups located downstream of the chamber. We decided to check the beamline again.

At 20:40 the detector was switched off. The turbos were then switched off. At 21:00 a tiny amount of air was allowed into the chamber to help slow the turbos, by 21:05 they were <12Hz. We vented the chamber.

After inspection of the beamline we discovered a new cause of the tuning problem. A small piece of mylar was in the bellow located downstream from FC-0. See attached IMG_2724.jpg.

We inspected the 12um mylar in front of the S2, it was not damaged, suggesting the rogue piece of mylar from the bellow is from a previous experiment.

We removed the rogue mylar and remounted the bellow to the beamline, we confirmed it was aligned using the telescope. We had a clear line of sight through the beamline, suggesting the problem is solved.

We declared victory.

At 22:30 we started the roughing pump for the section of beamline upstream from FC-0.

(Note: Tom Davinson is now in CIRCE until the 21st)

On 19/02/2018 we performed the following:

This morning we gave CIRCE technician Antonio slanted spacer boxes (for mounting preamps) and also the Al box (used for target ladder) for minor modifications

I needed to unmount the Al box from the target chamber. As I did so some air rushed in as I unmounted the box, indicating the chamber was not back at atmosphere from pumping on Friday.

I also removed the central lid with the iris attached. I discovered the iris was broken beyond repair. We will need to order a new one and some spares.

Learning note: To avoid damage always have irises fully opened when pumping down the chamber.

In the meantime Tom D has been wiring up the rest of the electronics setup. He discovered the CAMAC crate was not supplying any voltage. We removed the crate and double checked the connection between the rear power box and the crate – it was not fully screwed in on the bottom. After fixing this we remounted the CAMAC and found all voltages read out correctly, including a current readout of -10A at the -6V voltage.

Next we set out to vacuum test the chamber. In total today we performed four vacuum tests.

In each test the diode mount, lemo feedthrough, 64-way vacuum feedthrough, and an iris mounts were installed in the central section (the iris mount in the central chamber had no iris due to damage mentioned above). The iris mount with an iris (fully opened) and 64-way vacuum feedthrough were installed in the downstream section. The Al spacer box for the target ladder was also installed, however the target ladder was not because Antonio was not finished with modifications. Instead of the target ladder a blank flange was installed. The two actuators for opening and closing the irises were also installed in the central and downstream chamber sections.

The first two vacuum tests showed a high leak rate, high 10^-4 mBar even without helium injected close to the chamber.

In the first test we found the two 64-way vacuum feedthroughs were causing a leak, after venting the chamber these were removed and mounted flat to the lid using four bolts, one at each feedthrough corner. We then started the second test.

In the second test we discovered a leak was caused by the lemo vacuum feedthrough on the central lid. After the test we put additional grease on the o-ring and around the flange section of the feedthrough (atmosphere side) to help it seal.

On the third vacuum test after ~ 20 minutes of running the up and downstream turbos the pressures levelled to:

Up = 3.6e-4 mBar, down  = 3.4e-4 mBar

We then switched off the turbos and continued monitoring the vacuum. After ~30 minutes from turning off power to the turbos, they had completely stopped spinning, the pressures read:

Up = 6.5e-1 mBar, down = 6.5e-1 mBar

We found during this test the lemo feedthrough was still not sealing, and in addition neither was the Al spacer box for the target ladder.

After venting we found a hair on the lemo feedthroughs o-ring. The hair was removed and additional grease was applied to the o-ring and lid. We also confirmed the nut was tight. For the spacer box we found the bolts used were slightly too long, and so removed ~ 2mm from the threads. The box was then remounted and looked flush with the side of the chamber.

After this test at ~16:00 Antonio had finished and delivered both the modified spacer boxes for the preamps and the target ladder mounting box, now it correctly uses a 16mm centering ring.

We then started the fourth vacuum test, now with the target ladder actuator mounted too (as well as all the other parts from tests 1-3):

At 16:43 the roughing pump in the leak test was started. At ~16:50 the turbos were started, both up and downstream from the chamber.

At 17:04 (~15 minutes later) the pressures in the chamber read: Up = 3.1e-4 mBar, Down = 2.8e-4 mBar.

We declared victory for the vacuum and decided to mount the detectors and an alpha source.

On the central lid we mounted the Si diode with 0.9um mylar and a 1mm collimator at ~28 degrees rotation (relative to the central lid) -> currently this is performed using an angle measuring app on my android phone and one screw, so this angle selection needs to be better reproducible for the future.

We discovered there was no way to mount the S2 detector on the central lid -> either the legs of its connectors collide with the lid, or when the iris mount is rotated 180 degrees (moves detector slightly upstream) the iris then collides with the target ladder. The way we mount the detector on the central lad needs redesign -> I will take the central lid with irises and diode mount back to Edinburgh to address and fix this problem. I can also use this opprtunity ot find a better mounting procedure for the Si diode.

We did mount the S2 2323-18 (496um) detector to the downstream iris mount. 12um mylar was placed in front with a central hole of max width <20mm to allow the beam to pass trough.

On the target ladder we mounted an alpha source at position 5mm. The alpha source specifications are:

Type: EAX

Prod No: 111109-1242002

Radionuclide: 241Am + 239Pu

Activity: 8.153 kBq

Reference Date: 25/3/2010

At 20:49 with the single S2 detector, diode detector and the alpha source mounted in the chamber we started the roughing pumps.

At 20:54 we started the turbos, including not only the up and downstream turbos but also the large turbo located below the chamber. The pressures read: Up = 1.3e-4 mBar, Down = 1.5e-4 mBar.

We went to dinner. Raffaele had fish.

22:19 The pressures read: Up = 1.4e-5 mBar, Down = 3.7e-5 mBar

We mounted the preamp box on top of the chamber with preamp 2 inside. The cables for the detector bias, +15 and -15V preamp power, +ve pulser, and ribbon signal cables were connected.

Biasing the S2 to -130V we read a leakage current = 1.16 uA. Powering the preamp we read currents: V=+15V -> I = 0.9A, and V=-15V -> I = 0.4A, as expected. The pressures read: Up = 1.4e-5 mBar, Down = 3.2e-5 mBar

Using DSO we observe

• RAL 1 CH 0->7 pulser OK, no alpha
• RAL 2 CH  0 no pulser or alpha
• RAL 6 CH 1->7 pulser OK,  no alpha
• RAL 8 CH 6 no alpha, pulser not connected to n+n ohmic strips

We declared today a good day and left the lab.

This morning whilst I was setting up the ribbon cabling (see eLog entry #8) I was considering collecting a voltage bias vs leakage current curve for one/two of the S2 detectors, depending on time available.

This would involve using the central section of the chamber and the straight spacer box to mount the preamp on top of the lid.

Note: we currently cannot use the angled spacer boxes for the chamber yet, because these need to be trimmed by Antonio (the technician) to allow more space for the ribbon cables and also allow the box to sit flat on top of the vacuum feedthrough. We will be seeing Antonio on monday morning to prioritise required machine work.

However, I then remembered that after we stopped the pumps last night we did not vent the chamber. This morning at 10:52 the labview program used to control the pumps read the following pressures:

• Turbo Up 1 = 1000mBar
• Turbo Up 2 = 389mBar
• Turbo Down 1 = 86.1mBar
• Turbo Down 2 = 49.7mBar
• Chamber Up = 1000mBar
• Chamber Down = 139mBar

I emailed Lucio to see if he could come in this weekend to vent the chamber and we could then mount and test two of the S2 detectors, one after the other. Otherwise we can do this monday morning.

As an aside there is some serendipity here, the pressures I read this morning indicate if there is a leak in the chamber it is more likely to be found upstream.

Between 9:00 to 12:30 this morning Filipo was working on the weekend 14C measurements, allowing me to work in the lab during this period.

I unpacked four MALU 4532 Lecroy Logic Modules (sent to CIRCE two weeks ago). Three of these modules were installed into the 1434A CAMAC crate, which already had one module installed from the July 2017 shift. One module remains out of the crate as a spare.

I connected 16 way - 16 way ribbon cables between the front of both IDC converter boxes to the back of the RAL shaping amplifier modules. They are connected as follows:

• RAL shaping amps I, II, XI, and IV are connected to top convertor box inputs 0->3, counting from the left when facing the rack
• RAL shaping amps V, VI, VII, and VIII are connected to top convertor box inputs 4->7
• RAL shaping amps X, XII, XIII, and "R" are connected to bottom convertor box inputs 8->11
• RAL shaping amps "S", "Q", "u", and "W" are connected to bottom convertor box inputs 12->15

In second electronics rack, "Rack B", at the top is a Nim bin used last July 2017 for the Si diode.

In this nim bin I installed two NIM-ECL-NIM converters and the PB-5 Pulser Generator

Currently in the Nim bin from left to right we have the following:

1. Silena mod 7710 Quad Bias Supply
2. Ortec 571 Amplifier
3. Ortec 863 Quad TFA
4. Ortec 935 Quad CFD
5. Two ECL-Nim-ECL Converters, Model EC1600 by EG&G-ESN
6. Lecroy Model 622 Quad Coincidence Unit
7. PB-5 Pulse Generator

The Nim bin was switched on in this configuration, I checked the supplied voltages with a voltmeter. All voltages, -6, +6, -12, +12, -24, and +24V read correctly.

Next I installed 5m 34 way - 34 way ribbon cables labelled 0, 1, 2, and 3 into the back of the top convertor box, including the grounding cable. Now:

• Cable 0 in back splits into cables 0 and 1 in front
• Cable 1 in back splits into cables 2 and 3 in front
• Cable 2 in back splits into cables 4 and 5 in front
• Cable 3 in back splits into cables 6 and 7 in front

Next I installed 5m 34 way - 34 way ribbon cables labbeled 13, 14, 15, and 16 into the back of the bottom convertor box, including the grounding cable. Now:

• Cable 13 in back splits into cables 8 and 9 in front
• Cable 14 in back splits into cables 10 and 11 in front
• Cable 15 in back splits into cables 12 and 13 in front
• Cable 16 in back splits into cables 14 and 15 in front

The other end of these eight 5m long cables are ready to be plugged into the EDI preamps

I then plugged 16-way ribbon cables into the Analogue Output of the RAL shaping amplifiers in the following order, where ADC ... is the label of the cables:

• RAL I -> ADC 8A
• RAL II -> ADC 8B
• RAL XI -> ADC 9A
• RAL IV -> ADC 9B
• RAL V -> ADC 10A
• RAL VI -> ADC 10B
• RAL VII -> ADC 11A
• RAL VIII -> ADC 11B
• RAL X -> ADC 12A
• RAL XII -> ADC 12B
• RAL XIII -> ADC 13A
• RAL "R" -> ADC 13B
• RAL "S" -> ADC 14A
• RAL "Q" -> ADC 14B
• RAL "u" -> ADC 15A

Some of the RAL "W" Analogue pins were slightly off center. Filipo needed to leave so I left cable ADC 15B unplugged.

I attach photos of the current status of both electronics racks

By 16:40 I mounted all three chamber lids.

The central chamber lid includes the diode detector mount, the iris, a vacuum feedthrough, and an actuator with no hook.

The downstream chamber lid includes a vacuum feedthrough and an actuator with no hook.

I then mounted the target holder actuator with its two aluminium boxes.

I noticed the sides of the boxes were not trimmed down since my last visit in July 2017. So again I needed to remove washers from the bolts directly below these boxes, which are used to connect the beamline and turbo sections of the target chamber. I also noticed the hole of the aluminium box which the target actuator arm sits was not enlarged since my last visit, and so is not large enough to fit a standard 16mm o-ring centering ring. Instead a smaller centering ring is used which means the actuator arm is not centered, for the vacuum tests this isn't a big problem.

Note: when I mounted the target actuator I replaced its 80mm (total length) Al tube with the 60mm (total length) Al tube, this should allow access to all target positions.

After some further setup on the beamline - including checking the turbo pumps were being water cooled - we were ready to start the vacuum test.

At 18:00 we started the roughing pumps

At 18:10 we started the two upstream and two downstream turbo pumps

At ~18:18 the chamber up and chamber down readings were at low 10^-4 mBar, we would've expected lower pressure readings due to the power of the pumping system. We suspected a leak and switched off the pumps.

Lucio noticed the 70mm screws mounting the lids and collar to the rest of the chamber were too long, and either needed to be shortened or additional washers used - otherwise we could heavily damage the chamber thread

At the end of the day we learnt Fillipo will be in the lab tomorrow (saturday 17th) between 9:00 - 13:00, and agreed that I (Thomas C) could come in and connect the electronics cables ready for next week.

After lunch we were still having problems with the aperture hook, see first attached image highlighting the arm is located in close proximity (but not touching) the vacuum feedthrough and ribbon cable.

Meanwhile in Edinburgh Peter Black designed and built an additional component of the hook to assist in connecting it between the actuator and iris arms, see second attached image.

I decided enough time had been spent on this so far and to go ahead with testing the chamber vacuum.

This morning we moved the electronics rack to within ~2.5m of the target chamber, leaving room for the ribbons cables of ~5m length which connect the preamps to the amplifiers in the rack.

Then I continued in attempts to solve the iris arm problem, see eLog entry #3.

When comparing to the CAD drawing (entry #4) David pointed out the iris was mounted the wrong way around, and that it should be rotated 180 degrees. I attempted this yesterday but decided to investigate more thoroughly.

I made three changes in total:

1. I replaced the lemo cable on the Si diode with a shorter one (~7.5mm) from Edinburgh, reducing the chance to catch the lemo between the lid and chamber wall

2. I moved the diode mount away from the upstream chamber wall to be certain there was no collision here

3. I removed the nylon screws intended to connect the S2 to the nylon standoffs on the iris

After each change I reattempted mounting the central lid with the iris attached, after the third correction it fit! This suggested the nylon screws were slightly too long.

I measured the thickness of the S2 detector serial no 2323-18:

PCB board thickness = 2mm

Yamatchi connector thickness = 8mm

Bond wire solder thickness on back of S2 ~1mm

The thread of one nylon screw was cut from 6mm to 4.5mm, after screwing this back onto the iris standoff I found the lid still fit onto the chamber. There will be enough thread to still mount the S2's.

At ~13:20 we then went to lunch

Find attached the latest CAD diagram of the Target Chamber, drawn by Peter Black

After lunch we attempted to connect the actuator arms to the iris arm used to change the iris diameter. We need two iris diameters: fully open for experiment measurements and a 5mm diameter for beam focusing

To do this the original design uses a cuboid with two rods, one rod is connected to the actuator arm, and the other rod is connected to the iris arm with a hook - see attached. The rods were first cut down to fit into the chamber. This would allow us to change the iris diameter whilst under vacuum.

We decided to first check we could connect the hook to the iris in the central section of the target chamber, because this has the most amount of access space. We mounted the iris onto the bottom of the central lid using it's two legs.

After several attempts we could not find a suitable position for the hook and box combination, for several reasons:

1. The cuboid used to hold the metal hook will hit the iris legs at the limits of the actuator arms movement. This means the iris cannot be completely opened or closed. We could close the iris until a diameter of 13mm is left, however the active region of the S2 detectors starts at ~11.5mm diameter so this will not work when focusing the beam.

2. Also if we mount the hook facing upwards (above the cuboid) it is too high to reach the iris arm

3. If we rotate the hook such that it faces downwards (below the cuboid) it now reaches the iris arm. However, the hooks height needs to be adjustable because the iris arm moves vertically as the iris is opened and closed. This is currently not possible as the hook cannot be loosed without falling into the chamber

Note: when the iris is fully opened or closed its arm is at its furthest vertical distance from the chamber lid. When the iris is halfway between open (or closed) its arm is at its closest vertical distance from the chamber lid.

We noticed the cuboid used to hold the two rods is assymetrical and so attempted switching around the two rods, this did not solve the problem.

We then attempted a simpler solution: We replaced the cuboid and two rods with two long screws placed directly in the actuator arms threaded holes, see second attached photo.

The idea being that we can simply move the iris arm with these two screws - there will be some backlash to this technique because the distance between the two screws is larger than the diameter of the iris arm. This should not be a problem because we will only need two positions.

However we found the screws still collide with the iris legs close to the limits of the iris arm movement.

Most importantly: We realised that either the hook or screw technique will both hit the ribbon cable connecting the detector to the vacuum feedthrough, see attached sketch

The central collar of the chamber does have a second position for the actuator arm, however this will hit the Si diode we intend to use to measure the backscattered beam. So this will not work.

At 18:30 we decided to leave the lab and sleep on this problem.

The only solution seen so far is to focus the beam with no detectors mounted. Then after focusing is complete: vent the chamber, mount the detectors, repump the chamber down to vacuum, and remount the preamplifiers on top of the chamber. This would not be optimal but it may be a temporary fix until a better solution is found.

This morning both myself and Raffaele mounted the beamline section of the target chamber.

We also mounted the turbo located immediately downstream from the target chamber, see attached IMG_2621.jpg image - the beam will enter from the right of the image

We then mounted the collar section of the target chamber.

We mounted the two linear actuators onto the collar section, which are used to open and close the iris apertures.

These apertures will be essential to stop the beam during beam focussing

Attached is a report summarising work performed on the electronics and target chamber in CIRCE from the 10th to the 22nd July 2017.

Outstanding problems have also been listed.