Wednesday, August 24, 2016, 17:05

Target container was previously coated with TaC and sintered up to 1900C at 420A/7.01V

Container is loaded with beta-SiC 432 discs at 16cm in length. 

Container is wrapped with Ta-heat shield; no end-caps are used at this time.

Chamber is being pumped down.

 Thursday, August 25, 2016, 12:04

Chamber has been pumped down overnight.  Pressure at 5.9e-7 Torr.

HS water valve opened; no leaks were detected.

Sintering temperature 1800C. TGHT will be set accordingly to get the desired temperature.  TBHT max at 230A.

Thursday, August 25, 2016, 12:12

Tapped up TGHT/TBHT to 40A.  Vac at 7e-6 and slowly going up  but still below limit.

 Monday, August 29, 2016, 11:04

TGHT and TBHT reached to 250A (3.65V)//230A(3.02V), respectively, and kept stable over the weekend. 

Temp measured at 1372C with slope set at 1.04 (1230C at slope 0.98). 

No visible coating on windows. 

Setting up TGHT to reach 1800C; monitoring locally

 Monday, August 29, 2016, 14:35

Stepped up TGHT to 390A/6.54V; light coating was observed on the windows.  The temperature should be around 1800C which should be in line with the power (current) deposited in the container during the TaC coat sintering process (1900A at 420A); however, with the light coating the reading may be off.  

Mikron was used to measured inside of the tube (away from the discs); temperature was measured at ~1800C, (see attachment)  [adjusted slope at 1.00 to compensate the SiC disc and Ta]  

Omega was used to measured the temperature of the discs.  It is difficult to know what's the temperature inside the tube, so this measurement  is only taken as a guideline.  Slope changed from 1.04 to 1.15 to match Mikron's reading.  

After heated at  390A for 30 mins, the windows are now coated.  Temp reading is no longer reliable.  The temperature could be above 1800C.  Keeping a close monitor!!!

No blockage inside the tube was observed.  

Will remain heating at 390A/6.44V for overnight before proceeding with the re-conditioning. 

 Tuesday, August 30, 2016, 10:41

Target was heated at 390A  for over 10 hours and then cool down at 1A/min (see attachment#2).  Windows were fully coated and Omega couldn't register any reading. 

Chamber will be vented and target will be inspected before proceeding with the re-conditioning step.

Tuesday, August 30, 2016, 12:13  

Target was inspected; no visible damage was observed (see attachment)

Material coated on the windows and the cu heat shields;  all parts were wiped off with acetone. 

No visible material build up inside the container. 

Chamber is now being pumped down for re-conditiing.  

 Tuesday, August 30, 2016, 13:05

HS water valves open; no leaks detected.  

Vac at 3.6 e-6 Torr.  

Ready to set up TGHT/TBHT

 Tuesday, August 30, 2016, 16:41

TGHT/TBHT stepped up to 340A (5.40V) /230A (3.1V), respectively. 

Temperature was measured at 1835C at TGHT of 340A.  Omega, Mikron and analogue pyrometer were all reading ~1800C inside the tube (not on the SiC surface).  For that reason, I decided to stop the current at 340A, instead of 390A.  

TGHT voltage is running stable.  

No visible coating or blockage inside the tube was observed.  

Wednesday, August 31, 2016, 11:53

A thin layer of coating is observed on both the side windows (see attachment 5).  The temp reading is no longer reliable.

TGHT remains at 340A/5.45V.  P/S voltage is performing steadily.  

No clogging inside the tube is observed. 

Setting up another Omega reader to measure temperature from the front window since this window is clear and won't get coated (see attachment #6).

Temperature measurement from the front window is ~1140C; this corresponds to the measurement from the analogue pyrometer with the correction of e=~0.2 for tantalum at 1100C.

Note:  The temperature measurements should be taken as relative.  Since the reading from the side windows isn't reliable any longer, the centre window will give some information how stable the temperature is holding during the reconditioning process.  Continue to monitor.

 Wednesday, August 31, 2016, 16:24

About two hours ago, I increased TGHT to 350A and stayed there for a few mins (see attachment 7).  No change in temp was observed - that's mainly due to the coating on the windows.  As for the temp measurement from the center window, a more power current input would require to see the change as heat is slowly propagating through the layers of Ta heatshields.

Local inspection on the target: no clogging inside the tube. Voltage/Current is stable at 340A/5.45V.  Vac at 1.43e-7 Torr.

 Wednesday, August 31, 2016, 23:00

Strange observation:  Temperature readers on both omega have gone up. (see attachment 8).

I'm not sure if the temperature is reiiable.  I actually saw the increase in temperature ~1850C  last night around the same time; no change in TGHT current/voltage.  By the next morning, it went back down to 1400C with significant coating on the windows.

 Wednesday, August 31, 2016, 23:28

I had ISAC Op (Justin) to help me go into the Hotlab and take a look at the reading on Mikron.  Indeed, it is reading about 2000C which is close to the Omega reading.  He also looked into the tube through Mikron scope and found no clogging inside the tube.

To be safe, I am going to lower the TGHT heater down to reach ~1800C.

Wednesday, August 31, 2016, 23:41

Lower TGHT to 305A/4.81V; OMEGA reading at 1830C.  Vac at 1.27e-7 Torr.  Will remain at this current over night. 

 Thursday, September 01, 2016, 12:16

Checked on the target.  

Temperature readings, right windows (omega)= 1726C, centre = 1100C (omega), left (Mikron) = 1720C.  

No blockage inside the tube.  

TGHT stabilizes at 305A/4.79V.  Vac at 1.09e-7 Torr.  

 Thursday, September 01, 2016, 16:32

 About an hour ago, the temp dropped to 1660C with no change in TGHT current/voltage (see attachment 9).

Vac is a 1.06e-7 Torr. 

After consulting with Friedhelm, we decided to cool the target down and inspect it tomorrow.

Ramping TGHT/TBHT at 2A/min.

 Wednesday, September 07, 2016, 15:13

The target was removed from the Evap and inspected. 

Some spots on both ends and ionizer tube were crystalized.  (see attachment 10). 

No blockage inside the tube was observed. 

End caps were inserted.

The target was assembled and tested - All seems fine.