3 Was last in lab on 2012-09-20
4 - Left TCS experiment to take TCS of Si substrate
5 - Yesterday, briefly came in... program had crashed due to failed pressure reading
6 - Removed pressure reading from program, and restarted. But effectively, 6 days lost.
7 - The TCS now is very different to on 2012-09-20. I had hoped that I could see the gradual change.
8 - But program crashed after ~2-3 hours
10 - Check and compare electron gun parameters
13 # Venault Voltage = 10.34
14 # Accelerating Voltage = 264
15 # Focus Voltage = 8.17
16 # Deflection Voltage = 0.380
17 # Initial Voltage = sweep
18 # Heating Current = 1.149
19 # Heating Voltage (across filament) = 1.180
20 # Heating Voltage (across power supply) = 1.51
23 # Venault Voltage = 10.35
24 # Accelerating Voltage = 262
25 # Focus Voltage = 8.16
26 # Deflection Voltage = 0.382
27 # Initial Voltage = sweep
28 # Heating Current = 1.149
29 # Heating Voltage (across filament) = 1.174
30 # Heating Voltage (across power supply) = 1.537
32 Changes are negligable. => The surface has changed somehow over time
33 - Batteries of ammeter are also quite low though. Will replace and take new measurements.
35 - Curves now show 2 steep increases in current; 2 different surfaces in the beam?
36 - Si was originally cleaned very well. Only 1 steep increase in graphs on 20th, although possibly part of a second
37 - Maybe the surface has become contaminated (SiO2 layer?)
38 - A good way to check: Clean surface, do ellipsometry. Put surface in chamber, do TCS (without program crashing) over long period.
39 - Then take sample out, do ellipsometry. Fit for thickness of SiO2 and compare.
40 - I don't think I have time to do this.
41 - Position of first increase shifted to right (higher E)
43 - First: Fix problem in program if pressure is bad.
44 - I think I fixed it now. It required an embarrassingly small amount of work
45 - If pressure reading fails, defaults to "0.0". Which it will never actually be in real life, so I can tell which measurements failed.
47 - Give 602 new batteries
48 - Very slight shift in curve, but still clearly the same shape
50 - Keep gun properties the same; measure TCS of stainless steel to see what curve looks like
51 - Immediately note: Order of magnitude less current for stainless steel
52 - But, rotating the sample holder to ~300 deg = x10 current compared to 320 deg
53 - Ie: More current when sample surface is not perpendicular to axis of gun
54 - ??? Beam deflected horizontally by Earth's B field?
55 - Put to 320 deg; use same orientation as for Si
56 - Curve looks "unfocused"; no plateau
57 - First curve looks noisy. Subsequent curve looks smoother
58 - Leave for 10 mins. Curves show trend; higher max, and further to the right (higher E) as time goes on
60 - Test for response of Stainless steel sample to large steps in DAC level.
61 - Sample shows "charging problem" ie: exponential decay on steps