New Filament Tests Jan 2013

Initial settings

• Fil 2.40 A, Ext 5.8 kV
• 110.8 uA ext off
• gun vac 0.43 nT (4e-10 torr)

Gun on 10 kV

• pressure rise to 5.4 nT, 90.60 uA @ 10 kV

Probe Current Specs

• From SmartSEM manual
  
  • standard apertures 7.5, 10, 20, 30, 60, 120 um
  • currents 0.02, 0.03, 0.130, 0.300, 1.2, 4.5 nA
  • hi current approx double for off-center apertures

•  From acceptance tests - specs
• 10 kV, 6 mm WD, 30 um aperture, (same for VP)
• no condenser > 220 pA
• standard High current (with cond)  > 400 pA

• MF Supra acceptance
• 2.37 A, 4.85 kV ext
• 158 uA off, 133 10 kV
• 935 pA in high current

• OptiProbe upgrade early 2011
• up to 100 nA high kV
• ~ 40-50% at 5 kV

New Filament

• Jan 22 2013 tests @ 10 kV 6 mm WD
• 10 um 19 pA / 29.8 nA (!!!)
• 20 um 68 /135 pA
• 30 um 240 / 354 
• 60 um 730 / 1.46
• 120 um 2.96 / 5.92 nA
• 300 um 4.74 / 34.8 nA
• blanked < 1 pA

New filament standard/hi ratios normal, 10 um hi is impossible, must be aligned on 300 aperture
Aperture geometry:

• 30 um center
• 20 um above, 120 um below
• 300 top left
• 10 bottom left
• 60 top right
• blank position bottom right

Gun vac changes with beam voltage.

• At 10 kV was5.6 nT dropped to 5.4 over an hour, 
• 5 kB 6.9 nT drops to 6.7, 
• 2 kV 9.3 nT dropping. 
• 1 kV 10.6 dropping to 10.2 nT
• EHT off to 4 nT and dropping (current to 107.5 started 110.8)
• Let run overnight at 1 kV, 2.8 nT, still slowly dropping from 9 nT over 24 hours
• gun off drops to 0.95 nT
• Emission down to 71.8 uA, flattened out overnight
• EHT off 85.2 uA, was 110

• 5 kV 6 mm WD
• 10 um  14 pA 23.6 nA
• 20 um 50 / 100
• 30 um 187 / 258
• 60 um 550 / 1.09
• 120 um  2.22 / 4.44
• 300 um  3.5 / 26.0

• 2 kV 4 mm WD
• 10 10.7 pA  20.3 nA
• 20 43 / 84
• 30 160 / 210
• 60 446 / 889
• 120 1.77 / 3.66
• 300 2.85 / 21.9

• 1 kV 4 mm
• 10 10.2 (19.4 nA)
• 20 38 / 77
• 30 169 / 192
• 60 415 / 818
• 120 1.59 / 3.31
• 300 2.55 19.5

Overall image quality is pretty good, stable even at 1 kV

Wednesday tests after running 24 hours

•  1 kV @ 6 mm
• 10 8 / xx
• 20 30 / 50
• 30 140 / 149
• 60 315 / 626
• 120 1.18 / 2.53
• 300 1.8 / 14.8

• 10 kV @ 6 mm
• 14 / xx
• 51 / 102
• 179 / 261
• 545 / 1.08
• 2.20 / 4.41
• 3.5 / 25.88

Beam currents dropped 25 to 50 % depending on voltage & aperture.

Thursday afternoon

After EHT off since 1 pm wed, gun vac 3.9e-10, extractor up to 99.8 uA (from 85 just after EHT off
Try EHT on, gun vac up to 1.8e-9, ext 83.2 uA, 30 um 10 kV is 214 pA high 317
Drop to 1 kV, 3.8e-9 gun vac, 172 pA high 182
EHT off quickly, Ext now 100.0 uA, gun vac 5.3e-10

Friday morning

vac 3e-10 extractor increased to 107 uA over night.
1 kV on, vac to 3e-9, 89.4
185 pA for 30 um 1 kV

Current seems to be stabilizing as vacuum improves. Now around 3e-9 with 89.9 uA at 1 kV. Increase or decrease extractor by 100 V, current and pressure change in proportion.

Friday night around 20:40 gun switches off, no indication in log. Sys vac 6e-6, gun 1.7e-10

Monday morning restart gun (1/28/13)