On 05/04/18, after eLog #28

After the alpha calibrationrun Raffaele arrived and started beam tuning for 7Li 2+ at 5.0MeV using a LiO molecular source

We set the target ladder to position II (80.024 mm) - no target frame or target

Set downstream sperture to 82.5mm and central aperture to 85.5mm (iris diameter ~ 18mm)

Raffaele was struggling with tuning on accelerator end of beamline - decided to perform a pulser walkthrough

16:02 started DAQ for pulser walthrough, save name: 180405150720

Voltages covered: (Pulser amplitude setting)

• 1.4V
• 1.2V
• 1.0V
• 0.8V
• 0.6V
• 0.4V
• 0.2V

Note: pulser is daisy chained between both S2 preamp boxes (NOT diode preamp)

16:56 DAQ stopped, RT = 00:54:05, DT = 67%, Trigger Rate ~ 2kHz, Event mult = 53.1

At 16:57 the pressures read:

• TPU1 = 6.2e-6 mBar
• TPU2 = 9.1e-7 mBar
• TPD1 = 1.7e-6 mBar
• TPD2 = 1.7e-6 mBar
• CHUP = 9.4e-6 mBar
• CHDW = 2.5e-5 mBar

Checked detectors:

• Central S2 bias = -130.0V, leak I = 8.23 uA
• Diode bias = -70.1V, leak I = 0.00uA
• Downstream S2 bias = -130.1V, leak I = 2.44 uA

We opened the line valve, with no beam DAQ reads: DT = 8%, Trigger rate ~ 3400 Hz, event mult = 52.9

Beam tuning was performed with no target frame in the beam axis, beam voltage = 2.1358 MV

We had 1.2nA in FC 4, we supplied -400V to FC-E0 (FC immediately before chamber) for electron suppression

FC - 0 = 1.8nA (unsuppressed immediately after chamber)

We moved the target ladder to position I (3mm collimator)

FC-0 = 600pA

We need to use the ERNA magnet to bend the bean into FC-45 located after the chamber, this faraday cup is suppressed

CSSM magnet ON = 906.13mT, we noticed this section of the beamline needed pumping, switched on pump at 17:45

Received email from Tom D regarding noise, he suggested a few checks:

• Try changing preamp - feedthrough cable (currently have one spare which is wrapped in Al foil instead of copper tape - not ideal)
• Feedthrough - preamp cable drain wire should be connected to PCB at one end and the other left floating (both are attached to PCB at this time)
• Try isolating feedthrough - preamp cable from preamp lid - it may be touching

At 18:00 Raffaele needed to leave the lab, Jeremias could stay until 20:00, we decided to try and address the noise issue further

I switched off the detectors and preamp power, I removed the downstream preamp box lid and disconnected one end of the feedthrough - preamp drain wire (the end where the first 32 channels are connected on the PCB - connector P1)

I remounted the downstream preamp box lid.

The DAQ shows DT = 8% with 3kHz trigger rate.

To check the effect from the central S2, I tried setting the DAQ OR to only come from the central S2 and diode - I realised I could no longer see the pulser peak in the central S2 -> suggested central S2 trigger not working

I changed the cable between the 3rd and 4th MALU 4532 modules and the respective ECL-NIM converter -> now see triggers -> DAQ gives DT = 51% and trigger rate ~ 5.6kHz, but see pulser peaks in ADC modules 5 and 6

I considered only the downstream S2, setting pulser to 1.0V, RAL 1 CH1 amplifies this to ~5.5V with ~20mV noise.

Setting the DAQ OR to only come from this detector, the DAQ DT = 10% and trigger rate = 10Hz, event mult = 133.2. So it seems making one of the drain wires loose had a big effect on the noise.I decided to make the same change for the central preamp.

After switching off the detectors and preamp, I opened up the central preamp box and left one end of the drain wire on the preamp - feedthrough cable hangng loose. This is the same end as the one chosen for the downstream preamp.

Leaving the central preamp lid off, I reapplied preamp power and rebiased the detectors

• central S2 bias = -130.0V, leak I = 8.10uA
• diode bias = -70.0V, leak I = 0.01uA
• downstream S2 bias = -130.1V, leak I = 2.27uA

Checking RAL X CH1 (central S2) amplifiedoutput: 1.0V pulser output is amplified to ~5.5V with 50mV noise. Note the preamp box lid is off, so this looks promising.

I set the DAQ OR trigger to come only from the central S2, DT = 91%, trigger rate ~ 7kHz. High rate seen in ADC 6 channels 1->7 and channel 31

Changed DAQ OR to come from all 3 detectors, DAQ DT = 93% with trigger rate = 6700Hz, still see high rate in ADC6 channels 1-> 7 and channel 31

The time was 20:00 so we stopped for the day, it looks like the downstream S2 electronics is working fine, will check effect of mounting central preamp lid back tomorrow

All detector biases ramped down to 0V, preamp power off