The test stand holds up to 63kV, however at voltages over 54kV there are small discharges, rising to a continuous level around 60kV. The best guess right now is that these are coronal discharges coming from the end of the HV duct to the faraday cage. The only way to fix this would be to round out the edges of the duct, or to move the duct farther away. Since I have heard small discharges in other places, we may need to make a variety of modifications. Things that have had no effect:

1. Changing the EZL/EE voltages - break down is happening only between HV bias and ground

2. Cleaning the faraday cage

3. Locating sparks with a thermal camera

4. Conditioning - break down always happens at the same point

Tuesday, February 20, 2018, 09:01: Sparks at 62.5kV after a couple minutes. Sounds like they were in the EE spark gap but don't appear on the EE read current. Ozone smell around 61kV, so there are still some discharges.

Turned back up to 62.5kV but no sparks. Put it up to 63.5kV and there was a spark, but not in the EE spark gap as expected. Took down TP1B but everything is back up and seems fine.

Friday, February 23, 2018, 08:50

Friday, February 23, 2018, 08:53: BIAS / EZL / EE @ 62.5 / 29 / -1 kV

Friday, February 23, 2018, 08:56: Spark* Turbo pump TMS:TP6 restarted,

Friday, February 23, 2018, 09:13: Bias sitting at 61kV for about 15mins now. Still corona discharges from the area of the EE, but the area of the duct seems fine.

1. Al corona shield installed over end of the HV duct to suppress discharges from the sharp edge of the duct.

2. Some moving and shortening of cables to keep them from running close to different voltages.

3. Changed the angle bracket on the 3M bias-EE resistor chain to a plate, same position.

4. Moved the 164K EE resistor chain to sit flat against feedthrough K.

5. Moved the bias-EE spark gap to sit flat against the back of feedthrough K, required tapping a hole in the back of the copper clamp.

6. Cap and top of rack vacuumed.

7. Piece of shielding removed from top of HV rack

New parts installed. Corona Shield, brackets, and board/spark gap orientation.

Wednesday, February 28, 2018, 11:48: Power on. Ready to test

Wednesday, February 28, 2018, 14:00: BIAS / EZL / EE @ 30 / 13 / 1.5 kV

Wednesday, February 28, 2018, 14:06: BIAS / EZL / EE @ 40 / 17 / 2.0 kV

Wednesday, February 28, 2018, 14:11: BIAS / EZL / EE @ 55 / 24 / 2.8 kV

Wednesday, February 28, 2018, 14:16: BIAS / EZL / EE @ 60 / 28 / 3.1 kV

Wednesday, February 28, 2018, 14:18: BIAS / EZL / EE @ 62 / 30 / 3.2 kV

Wednesday, February 28, 2018, 14:21: BIAS / EZL / EE @ 63 / 31 / 3.2 kV

Wednesday, February 28, 2018, 14:26: BIAS / EZL / EE @ 65 / 32.5 / 3.2 kV

Wednesday, February 28, 2018, 14:32: BIAS / EZL / EE @ 66 / 33 / 3.3 kV

Wednesday, February 28, 2018, 14:35: BIAS / EZL / EE @ 66.5 / 33.5 / 3.3 kV ***2 sparks***

Wednesday, February 28, 2018, 14:37: BIAS / EZL / EE @ 66 / 33 / 3.3 kV

Wednesday, February 28, 2018, 14:41: BIAS / EZL / EE @ 66.5 / 33 / 3.3 kV

Wednesday, February 28, 2018, 14:44: BIAS / EZL / EE @ 67 / 33 / 3.3 kV

Wednesday, February 28, 2018, 14:47: BIAS / EZL / EE @ 68 / 33 / 3.3 kV

Wednesday, February 28, 2018, 14:49: BIAS / EZL / EE @ 68.75 / 33 / 3.3 kV ***Spark***

Wednesday, February 28, 2018, 14:51: BIAS / EZL / EE @ 68 / 33 / 3.3 kV

Wednesday, February 28, 2018, 14:57: *** 2 sparks ***

The BIAS was pushed to 69 kV however the resulting sparks shut down the communications with the test stand computer.

RPM0B was put into a continuous running cycle and had to be shut off manually.

The voltage was brought back down remotely via a separate computer. Turbo pump TMS : TP2 was also restarted.

Turning up bias, no corona discharge at 60kV but a spark at 61.5kV bias, 31kV EZL, -800V EE

Thursday, March 01, 2018, 10:26: BIAS / EZL / EE @ 65 / 32.5 / 3.2 kV

Thursday, March 01, 2018, 10:32: Spark* Knocked out turbo pump TMS : TP6 (Restarted) Communications restarted. RPM0A restarted.

Thursday, March 01, 2018, 10:44: BIAS / EZL / EE @ 61 / 30.5 / 3.1 kV

I have removed the resistor/varistor combinations that go between the poles of the target and tube heaters, and between those two supplies. I tested all the components to make sure they were still working after the sparks - for the record the varistors clamp at 23V, not 33V as implied by the schematic.

Tuesday, March 06, 2018, 10:48  BIAS/EE/EZL = 59.5/-1000/29.5  There was some kind of spark, the current on the bias supply went up to 400uA ( normally at 40 +/- 5 ) and the vacuum jumped a bit ( but still in the 10e-7 range ) but I didn't hear anything. It took out TP6 again. See first attachment.

Tuesday, March 06, 2018, 10:54  BIAS/EE/EZL = 60/-1/30

...

Problems

...

Tuesday, March 06, 2018, 12:00 BIAS/EE/EZL = 60/-1.5/29

Tuesday, March 06, 2018, 12:37 BIAS/EE/EZL = 62/-1.5/30

Tuesday, March 06, 2018, 14:11 BIAS/EE/EZL = 64/-1.5/31 No sparks but occasional ticking sounds from either the EZL or behind where the EE is... see second screenshot

Tuesday, March 06, 2018, 14:40 BIAS/EE/EZL = 65/-1.5/33

Test stand has been sitting at 65kV for about an hour now. Some small increases in bias power supply current but nothing significant (40uA). Some small sparks on the way to this voltage, and I ramped up very slowly. The corona discharges seen before seem to be related to the resistor/varistor combos since there are none now that I have removed them. Will redesign and reinstall.

The resistor/varistor combinations across the target + / -, tube + / - and target- / tube + have been remade and moved to the back of the power supplies to limit the corona discharges at higher voltages. Pictures attached.

First attachment: BIAS/EE/EZL = 63.25/-1.5/31 So far no issues.

Second attachment: BIAS/EE/EZL = 64.25/-1.5/32 Slight spark - bias current jumped from 40uA to 88uA and vacuum jumped from 2e-7 to 2e-6... Steerers went off.

Third attachment: BIAS/EE/EZL = 65/-1.5/32  Some small signs of instability in the bias power supply

Fourth attachment :  BIAS/EE/EZL = 65/-1.5/32  Been running for 20 mins now. More variation on the bias current output than at lower voltages but not too bad

Monday, March 12, 2018, 09:45: Gas lines opened. Leak rate set. Vacuum @ 1.16e-06T

Monday, March 12, 2018, 10:00: RGA on

Monday, March 12, 2018, 10:07: RGA off. Manually shut off power as well

Pressure:

Ramping up:

• Second attachment - bias at 50kV
• Third attachment - bias at 60kV
• Fourth attachment - bias at 65kV

Pressure has been slowly falling since we started this test - now down to 8.7e-7

Spark after 10 mins, see attachment 5. Very slight vacuum jump (8.5e-7 -> 1.2e-6) and bias current jump (36uA -> 113uA). Tripped TP6 and the steerers, as usual. Bias current read back more erratic afterwards (see sixth attachment).

System has been stable for 20mins, though current on bias is still more erratic than before the spark. Increasing He leak rate from 7 to 7.06 to bring vacuum back up to 2e-6 (see attachment 7). No effect from increased pressure.

Tuesday, March 13, 2018, 05:52: Power off.

Tuesday, March 13, 2018, 05:56: Waterlines purged

Tuesday, March 13, 2018, 05:57: Ion gauge, Turbos off.

Tuesday, March 20, 2018, 09:11: TMS:Q5 & TMS:Q2 controllers require repair. Unable to hold a negative voltage.

+ @ 680V

- @ 0V (Should be 680V as well)

Kyle L. & Rod N notified.

Tuesday, March 20, 2018, 12:58: The controller was fixed.

Tests on coil, temperature and the use of silver bolts.

(3) Vented silver bolts on the TBHT and (2) Full silver bolts on the coil

Wednesday, March 21, 2018, 14:10: Roughing.

Wednesday, March 21, 2018, 14:30: Turbo pumps on.

Wednesday, March 21, 2018, 14:35: Ion gauge on.

Wednesday, March 21, 2018, 14:42: RGA on.

Thursday, March 22, 2018, 06:52: Waterlines opened: Vacuum stable @ 3.04e-07T

Thursday, March 22, 2018, 06:53: Power/sources on.

Thursday, March 22, 2018, 06:56: IV4 Opened.

Thursday, March 22, 2018, 07:00: Auto ramping TGHT / TBHT to 580 / 200 A @ 2A per min.

Thursday, March 22, 2018, 07:04 : BIAS / EZL / EE @ 30 / 13 / 1.5 kV .

Thursday, March 22, 2018, 07:05: Optics on.

Thursday, March 22, 2018, 11:32: Out gassing noted. TBHT @ 200 A . TGHT @ 472 A. Ramping rate slowed automatically. Vacuum @ 3.03e-06T.

Thursday, March 22, 2018, 14:42: Out gassing continued. TGHT @ 570A.  Auto ramping TGHT / TBHT to 580 / 250 A @ undefined rate according to vacuum. Vacuum @ 3.03e-06T

Friday, March 23, 2018, 08:11: Auto ramping TBHT from 250 A to 290 A @ 2A per min. TGHT @ 580 A.

Friday, March 23, 2018, 10:20: Anode @ 100V & 8.5mA.

Friday, March 23, 2018, 10:28: Coil @ 50 A

Friday, March 23, 2018, 10:34: Anode @ 200V & 11 mA.

Friday, March 23, 2018, 13:08: RGA froze. Restart RGA

Sunday, March 25, 2018, 20:34 Vacuum stable @ 4.3e-07T . 

Sunday, March 25, 2018, 20:34: TBHT @ 290 A. TGHT @ 580 A.

Sunday, March 25, 2018, 20:34 :  Coil @ 50 A ^ 0.5 V

Sunday, March 25, 2018, 20:34 : Increasing Coil to 60 A

Sunday, March 25, 2018, 20:43: Vacuum seemed to increase to 4.4e-07T. 

Monday, March 26, 2018, 06:45: Optics on. Vacuum stable @ 4.38e-07T

Fernando

Wednesday, March 28, 2018, 08:31: Optics on. Vacuum stable @  3.57e-7T

Wednesday, March 28, 2018, 16:2: After increasing the coil current to to 75, A the coil voltage started to show an oscillating behaviour. (see image ttached)

When increased to 80 A the oscillatory behaviour increases. Reducing the current to 65A and then increasing it to 70 A showed a steady behaviour

Thursday, March 29, 2018, 15:51: Ramping down EZL, BIAS, and TGHT for the long weekend

Tuesday, April 03, 2018, 09:14: Vaccum at 1.77e-7T

Tuesday, April 03, 2018, 09:14 : Auto ramping TGHT / TBHT to 550/ 250A @ 2A per min.

Tuesday, April 03, 2018, 09:18 : BIAS / EZL / EE @ 30 / 13 / 1.5 kV  

Tuesday, April 03, 2018, 09:23 : Optics on

Wednesday, April 04, 2018, 08:39: Ramping TBHT to 290A @ 2A per min. TGHT remains @ 550 A

 Friday, April 6, 2018, afternoon: Due to inconsistencies on EPICS, Carla and I Change the Anode power supply to local in order to monitor the leakage current with a multimeter.

Monday, April 9, 2018, afternoon: TBHT@350A and TGHT@550A 

PS went current limited at AnodeBias=300V and show 3A on the PS Screen, the multimeter read the same.

Ramp down to 0 V 0A on PS. PS shows 0.01V

PS goes to limited current even at 2V.

Tuesday, April 10, 2018, 09:10: Problem persists even at lower TBHG (330A). 

The output cable was removed and the power power supply seemed to behave better. This could mean that there is a short inside the unit, in the past the anode cable had melted into the cup.

Planning to ramp down the TBHT and see if the behaviour remains. If it does, I would ask to remove the unit for inspection.

Tuesday, April 10, 2018, 09:32 : Ramping down TBHTH to 250A

Tuesday, April 10, 2018, 13:07 : Same behaviour. Cooling procedure started to see if the issue is still present, anf if it does remove unit for inspection

Wednesday, April 11, 2018, 06:44: RGA, power/sources confirmed off. IV4 closed. Ion gauge & turbos off.

Wednesday, April 18, 2018, 13:00: Post use comparison of the coil - A.S

1) Used coil from this FEBIAD = 1.999mΩ ***

2) Unused coil A = 2.421mΩ

3) unused coil B = 2.451mΩ

Started with Anode at 25V and coil at 0A, bias at 30kV. (attachment 1)

Ramped coil to 60A (0.4V) (attachment 2)

Ramped bias to 51kV, but then TP6 turned off and there was a momentary 0.2A decrease in the TGHT current. No spike in BIAS current seen, maybe TP6 is turning off for another reason? (attachment 3)

At 57kV, a small spark, heard outside the vacuum, sounding like it comes somewhere near the blue racks which hold the power supplies. It has sounded like that to me before. Did not turn anything off but bias current spiked from 110uA to 280uA. (attachment 4)

At 57.5kV another spark, taking down TP1B and TP6, as well as the CB1 steerers and TPS:Q1/2. TGHT current dropped momentarily from 581A to 240A, or so says EPICS. Maybe just a communications effect? Voltage for TBHT also dropped but nothing seen on TBHT. Coil current and voltage also showed small effects. (attachment 5)

After 10mins at 60kV, spike in bias current with slight spike in EE current but no other effects.

After 20mins everything has been stable, will turn the bias back to 30kV. As I turn the bias voltage down, the EE current ramps up. No change to EE voltage... (attachment 6)

Wednesday, April 11, 2018, 10:19: Roughing

New assembly & target. Same silver bolts.

Tuesday, April 17, 2018, 09:56: Roughing.

Tuesday, April 17, 2018, 10:57: Vacuum not coming down. @ 1.514T . Backing valves have been closed.

See* elog entry for roughing pump issue 04/17/2018

Wednesday, April 18, 2018, 08:57: Turbo pumps on.

Friday, April 20, 2018, 13:45: Power/sources on. RGA restarted

Friday, April 20, 2018, 13:46: IV4 Opened.

Friday, April 20, 2018, 13:50: Auto ramping TGHT / TBHT to 580 / 200 A @ 2A per min.

Friday, April 20, 2018, 13:56: BIAS / EZL / EE @ 30 / 13 / 1.5 kV . Spark @ Bias 28 kV knocked out RGA.

Friday, April 20, 2018, 13:59: RGA restarted.

Friday, April 20, 2018, 14:03: Optics on. Set

Friday, April 20, 2018, 14:40: Auto cooling TGHT / TBHT from 97 A @ 4A per min. Odd noise on (BIAS*) PS

Friday, April 20, 2018, 14:44: BIAS / EZL / EE @ 0 / 0 / 0 kV . Sources being turned off except TBHT and TGHT.

Monday, April 23, 2018, 10:46: FEBIAD TEST halted. See BIAS PS issue.

Tuesday, April 24, 2018, 10:46: Power off.

Tuesday, April 24, 2018, 10:48: RGA off.

Tuesday, April 24, 2018, 10:49: Ion gauge TSG:IG1 & Evap side turbos off,

Tuesday, April 24, 2018, 10:50: Ion gauge TMS:IG6 & beam side turbos off.

Tuesday, April 24, 2018, 10:54: Waterlines purged.

Tuesday, April 17, 2018, 10:57: Vacuum not coming down. @ 1.514T . Backing valves have been closed.

TSG:CG1A @ 1.515T

TSG:CG1B @ 1.529T.

Tuesday, April 17, 2018, 11:02: TSG:PV1 Closed. Roughing pump off.

Vacuum group notified.

Wednesday, April 18, 2018: Replace pump & adapters. Clean.

Wednesday, April 18, 2018, 08:45: Start TSG:RP1 and open PV1, BV1A  & BV1B

Wednesday, April 18, 2018, 08:55: exhaust pipe/mesh cleared out back

Wednesday, April 18, 2018, 08:57: Turbo pumps on.

RP status ok.

Thursday, April 19, 2018, 08:30: waterlines opened. No response on RGA. Vacuum @ 3.42e-07T

Thursday, April 19, 2018, 12:52: Pin J1 was reconnected into the anode power supply. All jumpers were put back to remote control.

NOTE: the cable EXTLKT is still not connected. I will ask Carla about this one.

Thursday, April 19, 2018, 18:00: Cable EXTLKT connected.

Thursday, April 19, 2018, 18:12  When turning the transformer on, the Anode PS was not turned on. Neither the TGHT.

Thursday, April 19, 2018, 18:30: I turned off everything. Will check tomorrow with someone. 

Friday, April 20, 2018, 11:01 : Issue fixed. I've attached a picture of the jumpers connection for future references

The fan in the EZL power supply is making a terrible noise - keep an eye on it, it sounds like it might give up soon.

Monday, April 23, 2018, 10:47: The back panel was opened. Original entry stated EZL power supply issue. Corrected to BIAS PS. High voltage group notified. Fan replacement required.

Monday, May 14, 2018, 13:20: BIAS fans, external an internal were replaced. Re-installed @ TS.

Monday, May 14, 2018, 13:26: BIAS ramped up to 10 kV. Response ok on epics and locally on the PS. No odd noise on the fans either. The issue appears to be fixed.

Ready for C-seals or FEBIAD work

Monday, April 30, 2018, 12:05: Roughing.

Monday, April 30, 2018, 13:11: Turbo pumps on.

Monday, May 07, 2018, 15:02: RGA, ion gauge, and turbo pumps off.