Fiber excitation

Excite fiber with direct beam normal incidence

ocean optics "vis 200 um" multimode

Slits full open, EMCCD 200 gain

Peaks at 455, 488, 650 nm. First two peaks easily saturate, reduced in point mode, increase with defocus. 650 peak is less flux dependent. Raster average over reduced area, signal drops with box size.

Charging present but does not seem to affect optical response.

Nothing on VPSE

Afternoon

When remounting fiber, glove catches fiber tip, fractures

Take spectra, also APD images after optimizing detector XYZ
30 um and 60um hi apertures

650 peak can see fiber core, less clear 480. Surface topography / cleave features have more effect on 480 image.

Record several images at 480 and 650 at 5 and 2 kV. Also connect PMT directly to fiber, no filter or spectrometer. Count rates to 1.8 MHz. Take several complete images no restarts.

Try using CT1 for PMT instead of CT2, now get some restarts.Back to C/T 2 runs OK.

Now take image at 1 kV for real (not 2 kV like before, one RHK mislabled 1 kV, first true 1 kV after 8 pm)

New filament continued Jan 2013

Monday

Gun on Monday morning after mysterious shutdown over the weekend.

Initial extractor current 84.8 uA, was 108 uA with beam off Friday afternoon.

1 kV, 73.8 uA, gun vac jumps to 1.8e-9 and rising slowly, 156 pA for 30 um standard aperture

After 30 min Iext up to 99.6, gun 4e-10
After 70 min, 88 uA at 5 kV, 2.25e-9 vac

Noon, ext 108.5 beam off, 7e-10 vac

Around 2:30 gun shuts down. This time got error "519 EHT Set Extractor Trip"

At 3:15 gun shut down again, no clear reason, no error message.

Gun runs through the afternoon. EHT off now 114.2, was around 94.5 @ 1 kV.

Turn on EHT 1 kV, see if it runs through the night. Now 8:30 pm.

Tuesday

This time gun did not shut down. Ext current relatively stable, starts 94.7 ends 95.5. Gun vac drops slightly, starts 3.0e-9 ends 2.7e-9

Gun off 115.3 uA, pressure 1.0e-9 within a minute.

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)