Wednesday, December 16, 2020, 10:30 (Carla) :

Started ramping up about 45 mins ago, now at 50kV with no issues. No sparking, occasional current draw to get to the next voltage step. Test piece is no longer drawing any current, as opposed to yesterday when it was drawing around 4uA at this point. Trace left on insulator must have partially evaporated in the vacuum overnight.

Wednesday, December 16, 2020, 10:34 :

Starting to draw some current at 50.5kV. Drawing 4uA at 55kV.

Wednesday, December 16, 2020, 10:51 :

Back up to 60kV, no sparks so far and no issues, though it is still drawing 5uA of current, as it was yesterday.

Wednesday, December 16, 2020, 12:28 (Alexander)

No sparks at 60 kV for 1.5 hours. Starting voltage increases again at 250 V increments. Currently limiting current to 6 uA. Current draw is 4 uA.

Wednesday, December 16, 2020, 13:20

63 kV. Appears current limited, increased current limit to 7 uA. First spark was at 62.75 kV.

63.25 kV. Seems current limited again but eventually reached a stable voltage after a minute. Increased current limit to 8 uA for next voltage increase.

63.5 kV. Spark.

63.75 kV. Unstable trying to reach voltage, appears current limited. Small spark followed by a big one on the rise of the previous. Second one activated something pneumatic nearby. Reduced voltage by 250 V. Looked at vacuum system but nothing abnormal.

63.5 kV. Spark, not recorded on GoPro. Stable after 5 minutes. Continuing.

63.75 kV. No longer current limited and reached voltage stably. Dumped data.

Wednesday, December 16, 2020, 14:02

64.5 kV. May be current limited again, took over a minute to reach stable voltage.

Note: None of the sparks recorded today so far have produced a response in the vacuum, which is holding steady at 1e-6 Torr.

65 kV. Smooth transition to it. Drawing 5 uA.

65.25 kV. Spark after voltage instability and current draw at 8 uA limit. Moved the Faraday cup, which made a sound. This is the sound I heard earlier. Lower current draw after the spark, back at 5 uA.

Wednesday, December 16, 2020, 15:20

Stable at 65.25 for an hour, no sparks.

Spark at 66 kV. Current limited and unstable voltage for about 2 minutes afterwards, then stable with current back to 6 uA.

Spark at 66.5 kV after some voltage instability and current limiting. Afterwards current and voltage returned to stability.

67 kV, two sparks, one right after the other. The second produced a bump in the vacuum. Reduced voltage. Brought back up easily; current stable at 5 uA.

67.25 kV. Spark. No instability preceding it for a good 20 seconds.

67.5 kV. Spark. Instability before, none after.

Wednesday, December 16, 2020, 16:08

68 kV. Spark. Instability before, none after. Vacuum dropped about 20 seconds after recovering. Current also dropped to 4 mA, at about the same time the vacuum dropped. Dropping current limit to 7 uA.

68.25 kV. Vacuum jumped back up to earlier values and then an eventual spark after some instability. Returned to stability after spark. Current now at 5 uA.

68.75 kV. Spark.

69 kV. Carla went to look inside. Saw some small sparks towards the back between the HV sheath and GND sheath in the small gap side. Very little registered in EPICS, though. Just a couple jumps in current and small dips in voltage. Not visible in GoPro footage.

Wednesday, December 16, 2020, 16:38

69.25 kV. Two sparks. Stable after second. Third spark. Reviewed GoPro footage because third spark was suspicious. Appears on video but not near or on the prototype. Could have been the wire. Dumped data.

69.75 kV. Some instability paired with a change in vacuum for the same duration.

70 kV. Carla went to look. Nothing visible on the StripTool but Carla said she saw small sparks towards the back. Going to leave here for 20 minutes before raising again.

Wednesday, December 16, 2020, 17:12

Held for 20 minutes at 70 kV with no action. Starting voltage increases again.

70.25 kV. Two and a half minutes of voltage instability, raised vacuum, and limited current. All of them stopped and started at the same time. Seems like conditioning to me.

70.5 kV. Carla saw two very faint sparks towards the back on the small gap side. Little appeared in EPICS. Spark followed maybe a minute and a half later. 2nd spark four minutes after that. Before and between those sparks the current was generally at 5 uA. About a minute after the 2nd, the current dropped to 4 uA.

70.75 kV. Short conditioning (response from all 3 monitors) period of about 10 seconds.

71 kV. 2 sparks one minute apart with some conditioning in between and after.

71.5 kV. Spark followed by 2 minutes of conditioning.

71.75 kV. One minute of conditioning.

Wednesday, December 16, 2020, 18:06

72.25 kV. Spark followed by a minute and a half of conditioning.

72.75. About a minute of conditioning.

73 kV. Instant spark followed by about a minute of conditioning.

73.25 kV. 30 seconds of conditioning then a spark. 1 minute of conditioning, then another spark, and conditioning done right after. Second one sounded like it activated the Faraday cup.

73.75 kV. Sporadic and weak conditioning? A few blips in voltage and current over about a minute and a half.

74 kV. Similar to previous but even less significant.

74.5 kV. Two minutes of conditioning.

Wednesday, December 16, 2020, 18:52

75 kV. 30 seconds of conditioning. Spark. 2.5 minutes of conditioning. 2nd spark. 10 seconds. 3rd spark; lowering voltage by 250 V for stability to capture footage of previous 3 sparks. Stable here for 5 minutes.

Wednesday, December 16, 2020, 19:01

75 kV. Nothing happening. Gonna leave for 30 minutes.

Wednesday, December 16, 2020, 19:31

75 kV for 30 minutes. No sparks or any other anomalies. Vacuum has been around 9.5e-7 Torr. Current hovering around 5 uA. Starting voltage ramp down.

Wednesday, December 16, 2020, 19:43

Ramped down. Nothing interesting. Turned power supply off in EPICS. Still on physically such that ramp up tomorrow can start remotely. Dumped data.