John Wong wrote:

John Wong wrote: Nikita Bernier wrote:  Thursday, March 29, 2012, 19:17   Target boat contains 3 BeO pellets : Sample,   Thickness (mm),   Mass (g),  Density (g/cm3) 1    9.06,  1.9713,  1.413 2    9.11,  1.9900,  1.416 3  13.54,  1.9916,  0.956   Samples 1 and 2 are made of BeO powder with 30% PVB which was washed with excess acetone and let to dry on a greased baking sheet (with PAM Butter flavoured). The flakes were then milled for 26 minutes at 400 RPM. It resulted in a very fine grey powder, much denser than the BeO powder with 30% PVB (not washed with acetone) that was used for Sample 3. The initial settings on Evaporator #2 were 100 A and 0.83 V until the vacuum increased. Evaporator #2 is now auto-ramping overnight at 1 A/min, up to 700 A, with the maximum voltage limited at 14 V, between 5.00e-05 (Good vacuum) and 6.00e-05 Torr (Bad vacuum).        Thursday, March 29, 2012, 22:31: TGHT tripped off a few times over the past hours.  After changing the Good Vac to 2.00e-5 torr and Bad Vac to 3.00e-5 Torr, the target heater are regulating properly and the max pressure is well maintained below 6.5e-5 Torr [Trip point @ 8.0e-5 Torr].  (see attachment#1: parameter.jpg) Friday, March 30, 2012, 23:19   Archive of the target current and vacuum over the past 24 hours.  (see attachment #1: archive_24hr) Saturday, March 31, 2012, 12:12 The organic materials have been burnt off.  The target heater ramping up is no longer restricted by the vacuum limit.  Archive of the target current and vacuum over the past 10 hours. (see attachment #2: TGHT@240A).   Saturday, March 31, 2012, 22:52 TGHT has stayed at 700A/12.37V, local @ 693A/12.43 = Temp @ 1780C.   The striptool shows some out-gassing when TGHT reached to 700A. (see attachment #3 marked with black circle: TGHT@700A.jpg) Increasing TGHT to 750A to see if there is any further reaction...   Sunday, April 01, 2012, 10:24   TGHT was ramped up to 750A, local 730A/13.90V.  The pressure has come down to low 10e-6 but not stable;  Some reaction may be ongoing therefore it's causing the vacuum excursion.  (See attachment #4: TGHT @ 750A).  Notice the current readback is not constant and it's slowly decreasing as the voltage readback is increasing.  There might be some resistant building up. --> Initiating the cool-down process at 2A/min.  Sunday, April 01, 2012, 19:30   TGHT has ramped down to 0A, and the pressure is going down (currently at 7.e-8 Torr) with no excursion.  (see attachment #5: TGHT@0A).  The chamber will be vented tomorrow, and the target materials will be inspected.

 Monday, April 02, 2012, 16:11

After sintering , the 3 BeO pellets have shrunk and feel robust.

The first sample ate through the Ta target boat, shrank a lot and has white and black marks. We suspect the PAM (mostly made of canola oil) to be responsible for the boat damage and the weird sintering process (see John's posts).

Sample 2 is holding well.

Sample 3, which was not washed with acetone, shows some cracks.

Sample,   Thickness (mm),   Mass (g),  Density (g/cm3)

1    -----,  0.6254,  -----

2   5.81,  0.9229,  1.032

3   8.89,  1.1073,  0.809

The average mass before sintering was 1.9843 g. After sintering, 0.8852 g. Thus the average mass loss is 0.9757  (49.0%).

We are starting a new batch of treated powder washed with acetone without PAM.