Beginning of May:
The cabling on the top of the test stand was changed to adapt for P2N testing. The TGHT and COIL PS were disconnected, and their DC cable terminals were connected instead to the TDK-LAMBDA P2Nheaters. The configuration on top of the ITS module is the following:
TBHT+ = A
TBHT- = B
MASTER+ = D
MASTER- = C
SLAVE+ = G/E
SLAVE- = F/H
Friday May 6th, afternoon
Once the pressure was almost stable in the low E-6 torr range, the first rampup was conducted up to ~600 A and the I,V parameters looked similar to previous P2N units. More tests to full current happening next week.
Monday, May 09, 2022, 09:29
P2N unit is being heated now, the automatic ramping utility is ramping the TDK-LAMBDAs while the TBHT is being increased manually.
Monday, May 09, 2022, 10:31
A voltage event happened, the TBHT voltage increased frmo 0.64 V to 0.73 V, while the P2Nheater dropped from 1.73 V to 1.56 V.
Monday, May 09, 2022, 12:19
At P2NHT=950A it was noticed that one leg of the P2N was glowing much more than the other, the ramping was first stopped and then ramped down.
Now the P2NHT=282A and TBHT=47A
Tuesday, May 10, 2022, 09:32
Test stand vented and target inspected, there is no obvious sign of damage or misconnection on the tantalum assembly. Some resistance measurements were taken across target elements and connections:
Screw on copper L to bottom flexy leg L = 117
Bottom flexy leg L to top flexy leg L = 24 / 0 (?)
top flexy leg L to bottom elephant leg L = 64
elephant L to elephant R = 360
top flexy leg R to bottom elephant leg R = 69
Bottom flexy leg R to top flexy leg R = 0 (?)
Screw on copper R to bottom flexy leg R = 125
Tuesday, May 10, 2022, 11:39
This morning, the target was inspected but nothing major was noticed, hence it was put back in the ITS for heating.
Tuesday, May 10, 2022, 17:40
Target being ramped: so far all good, total current in P2NHT=690A and TBHT=116A
A current measuring clamp was used to measure current in the 4/0 cables. The only bad thing is that the slave outputs half the current than the master, making the cables hotter (30deg vs 24deg).
Currents:
A-B ~116 A (TBHT)
C~468
E~124
G~102
Tuesday, May 10, 2022, 17:45
Event: reduction in P2NHT voltage and increase in TBHT voltage. After letting the PS ramp, it was noticed that the P2NHT voltage accelerated its increased, and the left leg started glowing like the previous time. The current was immediately ramped down, but still there was a voltage spike upwards in the P2NHT.
While the leg was glowing hot, the current between feedthroughs H (P2NHT-) and I (HV common) was 90A. Now that the "episode" is not there any more, the current is zero
Wednesday, May 11, 2022, 10:55
The previous P2N target had stainless steel screws at the bottom, where the copper L-shaped connector and the ta foil legs connect, which might have bene the cause of the gap opening and voltage increase. Now, the target manufactured for the previous beamtime is used, which does not have the cuts on the elephant ears but they are OK since don't interfere with the new IS cup design, and are ~3mm away from it.
Wednesday, May 11, 2022, 13:57
Start heating the new P2N assembly
Wednesday, May 11, 2022, 14:58
Stopped at
P2NHT= 501 A
TBHT= 95 A
All currents seem to be flowing in the right path, with no current in the jumper between H-I
Wednesday, May 11, 2022, 15:26
Voltage step in P2NHT and TBHT happened again. Current sum:
A = 125 A
B = 125 A
C= 470 A
D=474 A
E = 118 A
F= 85 A
G = 95 A
H = 132 A
Short G-E = 5 A
Short F-H = 3 A
Jumper H-I = 62 A
The most likely explanation of this jump is that the IS tip touches the plasma electrode as shown in the drawing below which would result in some current flowing through the jumper, more investigations are needed
Thursday, May 12, 2022, 08:19
Test stand opened, there is some sign of burn in the plasma electrode, but it's hard to say if it's because they were touching. Aaron added a tantalum 0.040" shim to the plasma electrode to distance it further from the target IS tube
Thursday, May 12, 2022, 13:20
ITS with P2N target installed and pumping down
Thursday, May 12, 2022, 15:50
P2NHT started ramping |