Thursday, September 29, 2022, 09:57

A Ta container tube was wrapped with 3 Ta heatshields.

338 graphite discs were loaded.

one Tantalum cup (modified to fit losely) was inserted on the front end along with a Ta spring.

on the backside there is no spring but four discs glued together with PVA

The system was left to establish vacuum over night.

Good vacuum set to5e-04Torr

Bad vacuum was set to 5e-2 Torr

Total weight of system including springs = 249.07 g

OMEGA slope = 0.99

The target will be heated to 2100 C, held there for 10 hours.  The target Temperature vs Power will be tabulated and the current required to reach 2100 will  be extrapolated to avoid using OMEGA at higher temperatures.

a)  The target will be removed, weighed and inspected

b) If the target boat is still good, run again at 10A higher than previous for 2 hours.

c) The target will be removed, weighed and inspected

d) i) If the weight is the same or negligible, experiment ends

  ii) if the weight has decreased and target still intact, repeat from step b and document all measurements and settings

 Thursday, September 29, 2022, 10:04

IGP1= 1.4e-04 Torr

TGHT= 80.0 A, 1.0V

Will allow pressure to drop and then continue heating

Thursday, September 29, 2022, 10:20

IGP1= 7.9e-05 Torr pressure on downward trend

Start heating at 2A/min to 200A

The target started dropping in temperature as current increased.  Suspected OMEGA issue.

Started cooling at -2A/min

Will continue next week.

Monday, October 03, 2022, 11:05

Upon inspection, the window though which the OMEGA laser travels was coated with dark precipitate (mostly a spot in the direct path of the laser).

Cleaned the window and started pumpdown.

Monday, October 03, 2022, 12:57

start heating @2A/20s = 6A/min because the target had previously been heated past additive evaporation point.

IGP1= 3.8e-06 Torr

Monday, October 03, 2022, 18:41

Will heat to 500A and leave for 10 hours.  The regression shows too high current to reach 2100.  Not reasonable.  So will work with 500A as a baseline.

Tuesday, October 04, 2022, 06:52

Temperature @500 A read 1742C

maintained for 10 hours

start rampdown at -2A/min 

OMEGA currently 1099C

Current = 500 A

Voltage =9.9 V

IGP1= 5.9e-7 Torr

Tuesday, October 04, 2022, 21:32

Quartz window was completely covered with graphite like dust.  final weight after heating = 244.57 g (a couple of discs came loose and they were weighed separately and not included in the next heating).

weighted target and added one extra heatshield because it looked like a lot of heat was escaping.  Will treat at 500A again for 2 hours.  The extra heat-shield should provide hotter environment.

new initial weight = 254.24 g (don't have a balance with greater precision .

Wednesday, October 05, 2022, 07:42

IGP1= 3.8e-07 Torr

ramping to 280A @ 3A/min

Wednesday, October 05, 2022, 11:40

ramping to 350 @ 3A/min

Then ramp to 500A

500A at 12:50

Wednesday, October 05, 2022, 15:52

ramping down at -2A/min

Thursday, October 06, 2022, 09:27

IGP1= 1.8e-07 Torr

Will dismount and weigh, then decide how to proceed

according to second regression, second heating was ~2000 C.  OMEGA not reliable after 1700 C in this case. 

Thursday, October 06, 2022, 12:34

The final weight after the second heating was = 254.19 g

reinstalled target and cleaned quartz window. 

will heat up to 510 A

Friday, October 07, 2022, 07:46

IGP1=  3.0 e-07 Torr

ramp at 2A/min to 500A.  will pause to take data points for regression.

Friday, October 07, 2022, 13:05

Start rampdown after two hours at 500A, 10.3V

-2A/min