The left (inside ring) bellow for the motors rod was replaced.

Replacing the bellow involved;

• One person holding the metal plate the detectors are mounted on (cabling remains plugged in) while the operation is performed. 
• The motors box is supported by the cryring crane by its mounting points
• Bolts on the flange connecting to the chamber can then be undone. The whole motors section (rod included) is then moved out of the chamber using the crane and someone to stabilise the rod as it slides off the detector plate. 
• Once off the chamber, the steel cover can be removed by disconnecting from the flange and from the motors box. Best to perform on a table. 
• The bellow is then removed by removing the nuts on the small flange (kf 25) connecting the bellow to the box. The bolts for these bolts are very long and go through the motors box from the moving metal plate seen in the attached image. 
• Follow these steps in reverse to install the new bellow. 

While replacing the bellow, it was noticed the long bolts for the small flange were too short. It was therefore very difficult to re-attach the nuts with any torque. The thickness of the head of the bolts was shortend to effectively lenghten the bolt which was sufficient to tighten the nuts. New bolts should be bought in case of replacing the bellows again. 

The leak on the actuator arm bellows has been attempted to be sealed using UHV vacuum seal spray. The spray had the opposite to the desired effect and the leak rate increased. When spraying with helium the leak rate had increased to 1e-9 mbar l/s. After lunch a second application of the vacuum seal spray was attempted, however the leak was not sealed. The base leak rate had also increased to the 1e-10 level up from in the morning and yesterday. With the leak increasing in size and risk of a full failure, we are no longer able to move forward with the bakeout. 

The chamber has been vented and we will move forward with plans for replacing the bellow tomorrow. 

Attached plot shows the most current pumpdown.  

CARME and the interaction chamber have been pumping for ~26 hours, P=4.15e-7 mbar, attached figures show the current pump down plot in comparison to the two previous pumpdowns in the last 2 weeks and the pump down with the bare chamber in 2020. The gradient of the pressure reduction appears to be improving for each pump down, either due to conditioning of the chamber or the reduction in leaks.  

CARME and the interaction chamber were leaked tested again today. The base leak rate has reduced significantly from 1.5e-10 mbar l/s to <1e-12 mbar l/s. All flanges on the interaction chamber were tested. A leak is still visible on the gate valve, however the magnitude of the leak has decreased significantly from 2.2e-10 to 2e-11. No other leaks observed on the interaction chamber. 

All flanges on CARME checked again, no leaks observed on flanges or wire seal. Leak was observed on the bellows of the left hand side (inner ring) actuator arm. Leak is not on either the small flange box side or the large flange on the chamber, but on the bellows itself. Image attached. Leak rate is 2e-10 mbar l/s. The actuator was moved with the pneumatic motor once to observed any effects, no effect on leak rate or the chamber pressure.

 Replacing the bellows is very challenging and will likely require removing the detectors installed on the rod. Current plan is to continue with the baking and re-evaluate post bakeout. The bellows will be baked but should not experience the same temperatures as the flanges on the chamber. Future experiments do not require extremely forward angles so that the actuator arm can remain fixed in place to not cause a n increase in the leak, the leak rate can be compensated by the large neg pumping power. 

This morning the pressure achieved was 1.44E-7 mbar. Leak testing showed an overall leak rate of 1.5E-10 mbar l/s, this is below the previous leak rate but still significantly above the leak rate from elog 141 of the CARME chamber on its own. Spraying helium, a leak is visible on the VAT gate valve on the interaction chamber (inside of the ring). The leak rate increases to ~2.3E-10 mbar l/s. No increase in the leak rate was observed elsewhere on CARME or the interaction chamber. It was decided to vent again and replace the gasket and inspect the knife edges for the valve. 

The valve was removed and the gasket was replaced. Several scratches are visible on the gasket which may be the cause of the leak (or damage may have been done during dismounting). While vented, the backing line was re-organised. The scroll pump is now on the outside of the ring for easier access (see attached image), the turbo pump was rotated to move all power cables and the backing line to the outside of the ring. 

CARME and the interaction chamber were pumped down again and the ion gauge was activated. Vacuum can be followed via the vac plot or by grafana on the carme-gsi computer (anydesk required). 

26/06/23

This morning the pressure was 4e-7 mbar. The bolts on the windows and the large flange on the bottom of the interaction chamber were tightend. No leak was present on the windows following tightening. However, the leak on the rotatable flange, although decreased in magnitude, was still in the 1e-9 mbar l/s range when helium was sprayed. The torque on these bolts was 36 Nm, which is already past the 33 Nm recommendation for M8 bolts. It was decided to vent the section and examine the flange. 

Tomorrow morning the gasket will be replaced and we will begin pumping again in the afternoon. 

27/06/23

Flange was removed and examined. Several scratches on the surface of the flange including on the knife edge were visible. These scratches were sanded away by the grossmontage and the flange was remounted. CARME was pumped down in the afternoon. Pressure was in the 1.5E-3 mbar range when the scroll pump stalled causing the pressure to increase and the turbo to increase in current to keep up. Error symbol was observed on the scroll, unknown to why it stalled. VAT gate valve to the chamber was closed and all pumps turned off to be safe, P~ 1mbar. 

28/06/23

Jan started the scroll pump on  just the backing line using the gas balast to see if too much water was pumped. Scroll running fine so the gate valve to the chamber was opened and the turbo started. 

The motors were moved using the pneumatic only, in and out for several cycles to gauge the effect on the vacuum. For the left arm no change in pressure was observed. For the right arm a small increase of 0.04e-7 mbar was observed which was quickly reduced by the turbo. 

The detectors were then biased to see if movement had any effect on the leakage current (large effects were observed in 2021 beamtime). Movement of the pneumatics saw no observable change in the leakage current above normal fluctuations. 

Both motors arms had been sucked into the chamber by 5-10mm due to the vacuum before starting the movement cycle. After one movement cycle, the motors returned to their normal fully out positions and remained fully out. 

23/06/23

Pumpdown started with the scroll pump 17:15 . The turbo-pump was started 17:55. Gate valve was closed and the turbo turned of at 19:20 due to no working fan on the turbo. 

24/06/23

Ion gauge was activated at 11:56, P= 3.7e-5 mbar. Attached pump-down curves begin from when the ion gauge was activated.

The first plot is a comparison was a calculation for water outgassing in the chamber (which has many assumptions) but is a good guide on the expected 1/t decrease in pressure over time. The second plot is a comparison to previous turbo pump-downs in 2020 and 2021. In 2020 the chamber was bare with no instrumentation. In 2021, kapton and detectors were installed, but the pump down was conducted in several stages. Pressure readings are taken from the gauge reader in the cave, the vac plot viewer online appears to show a slightly different reading. 

 25/06/23

10:30 P= 7.11e-7 mbar. Opened valve on leak cart and saw a large increase in the pressure (above ion gauge level). Closed valve to leak cart, pressure recovered quickly (1.28e-6 mbar after ~ 30 mins). Pressure in the leak cart ~3e-3 mbar. Possibly small trapped volume between valves on the leak cart. Opened valve to leak cart again, no pressure increase observed in the chamber.  

11:40 Leak testing. Base leak rate ~5-6e-10 mbar.l/s.  Spraying helium on the seal between the bottom of the interaction chamber and the newly installed valve saw a large increase to  >1e-8 mbar.l/s. Closer attention suggests the leak may be from the rotatable flange on the bottom of the interaction chamber. An increased leak rate to 1e-9 mbar.l/s was also observed on the diamond window on the inside of the ring. Spraying around wire seal and feed-through flanges on chamber on the inside of the ring gave a leak rate of 6e-10 mbar.l/s. This may be a small leak, but is most likely noise on the leak detector or drifting helium to the large leak on the interaction chamber. Cannot determine prescence of small leaks while the large leaks are active. Closing valve to leak cart saw the leak level drop to <1e-12 mbar.l/s. 

Attached images show sites of the major leaks on the interaction chamber. 

Attached are images showing the messages for normal turbo-pump operation

23/06/23

The CARME chamber and interaction chamber were connected and section 9 has been fully closed. New valves have been installed on the interaction chamber, in addition to new diamond windows. A leak cart has been connected to the backing line of CARME. Before begining the pumpdown, the manual valve between the interaction chamber and the electron target was closed. 

The pumpdown was started at 17:15,  the valve on the scroll pump was very slowly opened to not damage the berylium window. By 18:00 a pressure of 1 mbar was achieved and the turbopump was activated. By 18:20 a pressure of 2E-3 mbar was achieved, the ion gauge was activated and briefly flashed 5E-4 mbar but this is over its limit so the gauge shutdown. At 19:20, 1.3E-3 mbar was achieved, the ion gauge was activated but the reading was 1.7E-4 mbar which is still over its limit. The turbo fan was not working and temperatures on the turbo were ~50C and increasing, so it was decided to close the main gate valve and turno off the turbo overnight in order to fix the fan.

A bias test of the detectors was also performed while in vacuum, T=20.5 C. All detectors show expected V-I curve and the leakage current is ~1-2 uA lower than the previous test in air, probably due to reduced light leaks. The top right detector did initially produce >10 uA at 20 V but the adaptor card was not properly seated on the p-n feed-through. Seating the adaptor card correctly yielded the expected V-I curve. Further inspection of the pins on this feed-through will be performed tomorrow.  

24/06/23

Overnight the pressure had increased to 0.8 mbar. Opening the gate valve decreased the pressure by an order of magnitude. The turbo fan was fixed and the turbo was re-activated, the pressure dropped to 1E-3 mbar level within 20 minutes.  Ion gauge was turned on after 30 minutes with a pressure of 3.7e-5 mbar. Pump down plot and comparison to previous pump downs will be uploaded in a seperate elog. Turbo pump maximum temperature reads 46C and has been consistent for several hours. 

V-I tests completed for the right hand side detectors. Leakage currents ~0.4 uA higher than yesterday which is consistent with the increase in temperature of ~ 0.5-0.7C. 

The wire seal has been tightend further to 160 Nm. Open neg feed-through flange has also been fully tightend. 

The CARME chamber was then slid back onto the aluminium frame on the ring. Two carriages were damaged during the sliding process, which have now been replaced. Carriages were replaced by lifting one end of the upper frame section using the crane by only ~1mm. This was sufficient to slide out the broken carriage and replace it (see images to be uploaded)..  It appears there is some deformation in the rails on the temporary frame as CARME is slid across, which resulted in the damaged carriages -> further refinements are required for future slidings. The height of the chamber has been checked using the laser allignment.  

The turbo pump has also been mounted to the top of the chamber . Current plan is to close to the interaction chamber tomorrow and begin pumping.  

Internal CARME installations complete. 

• New strain reliefs (flange side) installed on each cable harness.
• 2x sets of SAES UHV1400 NEG pumps installed and connected to 2x power feed-through flanges -> continuity checked OK -> 3x UHV1400 modules gives a resistance of 7.4 Ohms, 2x UHV1400 modules gives resistance of 4.8 Ohms. 
• Pins B & D open circuit wrt ground ( DMM OL > 20M ? )
• Pin C connection to ground OK 
• Internal thermocouples connected. Middle thermocouple connected to strain reliefs, right thermocouple connected to a standoff on the detector, left thermocouple floating (see attached images). Resistance on thermocouples checked for middle and right thermocouples ~ 4 Ohms per thermocouple. 

V-I tests performed prior to closing CARME. All detectors show expected curve, but light leaks are present. Pressing my hand against the aluminium shield yielded 0.5-1.5 uA drop in leakage current. Could not turn off lights for the test due to other people working in the cave. Will repeat test when closed. Temperature in the cave ~ 21.5 C. 

Both chamber sections have now been closed. Wire seal appeared correctly positioned immediately prior to final close. Bolts closing the wire seal have been tightend to 100 Nm, plan to increase to 140 Nm tomorrow. DN100 feed-through flanges have been tightend with a torque of 24 Nm. 

Plan is to move chamber back onto the ring tomorrow and get ready for leak testing. 

Hopefully we will not be opening the chamber for quite some time so find attached images of all four installed detectors and a video of them both moving into the beam axis for future reference

Strain reliefs on the flange side of the cable harness have been installed for two detectors (top right and bottom right detectors). 

We require the strain relief parts from edinburgh in order to install strain reliefs for the left two detectors. 

Find attached images for the strain relief installed and a video of the clamped cables during a movement cycle.

A V-I test was performed for the two detectors which have all strain reliefs installed (see attachment 4).  V-I curve appears similar to the previous test (elog 398). Aluminium foil shield is now a bit battered so may have some small light leaks. Detectors were moved using the motors while bias was applied at 150V. Small change in leakage current observed (~0.01-0.02 uA)

The detectors were moved into the beam axis using the motors to check the maximum distance they can be moved in without collision with one another. 

Movement of both pneumatic motors results in a separation of ~ 4 cm between the detectors.

The servo motors for left and right were each moved in by 1 cm -> results in separation of 2 cm between the detectors

The servo motors for left and right were then each moved in by 5 mm -> results in separation of 1 cm between the detectors

The separation between the jacking plate of one of the detectors and the side of the adjacent detectors is closer than the separation of the detector silicons. The detectors could not be moved in any further than this to avoid collisions from the jacking plate

Attached are photos after movement of the detectors. Parallax may affect the distance on the ruler in the photos. 

During beam time -> Maximum distance that can be moved on the servo motors is 30 mm combined for left and right. (15 mm left and right or 10 mm left, 20mm right etc)  

The new MACOR strain reliefs on the (detector side) have been installed. See attached photos

The two pieces  of MACOR are not fully closed but we are confident that the kapton wires are sufficiently clamped.

In order for the strain reliefs to be installed in the correct poisition, two nuts on the jacking plate of the cable harness had to be removed. This is as the groove in the strain relief was not deep enough to accomadate the nut. 

Attached is also a video of the wires (not) moving with the strain reliefs mounted

08.35 DSSSD#3 bias -149.95V leakage current -6.418uA temperature +19.6 deg C ( https://web-docs.gsi.de/~lestinsk/tempplot.php )

DSSSD#3 bias OFF

12.44 DSSSD#3 bias -149.95V leakage current -6.448uA temperature +19.7 deg C ( https://web-docs.gsi.de/~lestinsk/tempplot.php )

CRYRING cave lights ON - leakage current measurements @ 60s intervals

6.448
6.449
6.448
6.448
6.449
6.448
6.448
6.448
6.449
6.448

18.24 DSSSD#3 bias -149.95V leakage current -6.442uA temperature + 21.0 deg C ( https://web-docs.gsi.de/~lestinsk/tempplot.php )

CRYRING cave lights ON - leakage current measurements @ 60s intervals

6.441
6.441
6.441
6.441
6.441
6.442
6.442
6.442
6.440
6.441

12.34 DSSSD#3 bias -149.95V leakage current -6.763uA temperature +21.2 deg C ( https://web-docs.gsi.de/~lestinsk/tempplot.php )

CRYRING cave lights ON - leakage current measurements @ 60s intervals

6.763
6.764
6.764
6.765
6.767
6.767
6.767
6.767
6.768
6.769

12.48 CRYRING cave lights OFF

13.03 leakage current -6.771uA - no obvious change due to the CRYRING cave lighting

17.31 DSSSD#3 bias -149.95V leakage current -6.658uA temperature +21.0 deg C ( https://web-docs.gsi.de/~lestinsk/tempplot.php )

leakage current measurements @ 60s intervals

6.656
6.655
6.655
6.655
6.654
6.652
6.652
6.651
6.650
6.649

CRYRING cave temperature variations/cycles ~0.1 deg C at +21 deg C ambient temperature can produce leakage current variations ~60nA for a leakage current of ~6.6uA

td@winder:~/f77$ ./jgen
 *** Enter reference temperature (K)
294
 *** Enter minimum temperature, maximum temperature
 *** and temperature increment (K)
290 298 0.1

 Temperature (K)   Ratio (J(T)/J(294.0))

      290.0                0.702
      290.1                0.708
      290.2                0.714
      290.3                0.721
      290.4                0.727
      290.5                0.734
      290.6                0.740
      290.7                0.747
      290.8                0.754
      290.9                0.761
      291.0                0.767
      291.1                0.774
      291.2                0.781
      291.3                0.788
      291.4                0.795
      291.5                0.802
      291.6                0.809
      291.7                0.817
      291.8                0.824
      291.9                0.831
      292.0                0.839
      292.1                0.846
      292.2                0.854
      292.3                0.861
      292.4                0.869
      292.5                0.877
      292.6                0.884
      292.7                0.892
      292.8                0.900
      292.9                0.908
      293.0                0.916
      293.1                0.924
      293.2                0.932
      293.3                0.941
      293.4                0.949
      293.5                0.957
      293.6                0.966
      293.7                0.974
      293.8                0.983
      293.9                0.991
      294.0                1.000
      294.1                1.009
      294.2                1.018
      294.3                1.027
      294.4                1.036
      294.5                1.045
      294.6                1.054
      294.7                1.063
      294.8                1.072
      294.9                1.082
      295.0                1.091
      295.1                1.101
      295.2                1.110
      295.3                1.120
      295.4                1.130
      295.5                1.139
      295.6                1.149
      295.7                1.159
      295.8                1.169
      295.9                1.179
      296.0                1.190
      296.1                1.200
      296.2                1.210
      296.3                1.221
      296.4                1.231
      296.5                1.242
      296.6                1.253
      296.7                1.263
      296.8                1.274
      296.9                1.285
      297.0                1.296
      297.1                1.308
      297.2                1.319
      297.3                1.330
      297.4                1.342
      297.5                1.353
      297.6                1.365
      297.7                1.376
      297.8                1.388
      297.9                1.400

STOP *** Program ends

Since yesterday evening, the bottom right detector was at -150 V. In the morning, the current was quite stable ~ 6.77 uA. The bias was switched off, the foils opened, both of the detector arms were moved in and out three times, and the chamber was tightly covered again. A negative bias voltage was applied from 0 to 150 V in steps of 10 V one by one to all four detectors, and the V-I results can be seen in Attachments 1-4. All detectors seem to be fine. The variation of the current with time at a constant bias voltage of -150 V was checked for all detectors and the results are in Attachments 5-8. Also, with an applied bias voltage of -150 V to the bottom right and left detector, the detector arms were moved in and out three times which showed a variation of 1-2 nA and 1 nA in the leakage current. For further conditioning of the bottom right detector, it is again left with a negative bias voltage of 150 V over the weekend.

Today, the foil was opened, the pins on the bottom right detector were checked and looked fine, the right-hand arm was moved a bit in and then out, and the foil was tightly closed again. The negative bias voltage was applied from 0 to 50 V in steps of 10 V. During the measurement, the lights in the cave were switched off to ensure no leakage current from the light*. The results are shown in Attachment 1. To condition the detector, it was left at a negative bias voltage of 50 V for ~ 3 hours with lights on. No increase in current was seen (see Attachment 2), indicating the chamber was nicely covered with foil. Then the negative voltage was increased from 60 V to 150 V in steps of 10 V. No large current readings, like yesterday, were seen today (see Attachment 3). The detector was then left at -150 V for ~ 30 minutes with the current to be nearly stable with fluctuations in the range of 70-100 nA. The foil was then taken off to check if there are any dust particles on the detector surface. As can be seen in Attachment 6, some dust particle was found at the bias/multi-guard ring (MGR) boundary structures of the DSSSD. The area was then nicely cleaned with isopropanol + lab tissue wipe (see Attachment 7) and the chamber was covered with aluminum foil again. The negative bias voltage was applied from 0 to 150 V in steps of 10 V again and the results can be seen in attachment 5, indicating the response of the detector to be normal, unlike yesterday. Before calling the day off, the detector was left at -150 V overnight.

* Every time, before switching off the lights, it was checked that no one else was in the cave.