Laura Lambert wrote:

John Wong wrote: Laura Lambert wrote:  Monday, June 29, 2015, 16:17 Target container is coated with TaC. No Ta-heat shields are used. TGHT will be ramped up to 580A at 0.2A/min. TBHT will be ramped up to 230A at 01A/min. Chamber is currently being pumped down.    Monday, June 29, 2015, 23:37 Opened the HS valves around 5pm.  Small leaks or just a vibration in the pipe line caused a rise in vacuum.  Leak rate is small, so allow the chamber to continue to pump down over night. Sintering process can begin tomorrow if vacuum is allowed.    Tuesday, June 30, 2015, 08:22 IGP1 = 3.6e-7 Torr. Tapped up manually to 40A. Vacuum looks good. IGP1 = 6.9e-7 Torr. Inititating auto-ramp...  Thursday, July 02, 2015, 09:56 IGP1 = 8.9e-7 Torr. OMEGA = 1728C TGHT and TBHT = 580A and 230A respectively. Tapping up manually to 1800C.  Thursday, July 02, 2015, 11:02 TGHT = 615A, 10.9V OMEGA = 1800C IGP1 = 1.1e-6 Torr. Will continue to heat for 4hrs.  Thursday, July 02, 2015, 15:43 Target container remained at 1800C for 4hrs50min. Initiating auto-cool for TGHT = 2A/min and TBHT = 1A/min.  Friday, July 03, 2015, 08:24 Vented in air and opened up this morning. Edge of container on both ends not fully sintered [see photos]

 Monday, July 06, 2015, 11:54

Inner tube surface isn't homogeneously sintered with TaC (see attachment).  

A second coating may help.  

For the re-sintering process, the target container will be wrapped with 6.2cm Ta (width) foil as a layer for heat shield on each side of the tube,  excluding the centre block - just like the same process was done last time, see e-log ID#217.  

The Ta-foil and the target tube will be spaced with Ta wire coiled around it.  

TGHT can be ramped up about 520A/9.1V to achieve 1900C.  Heating time for 3-4 hours until vacuum comes down to low 10-6 Torr.