SCA Channel 1 not Working

• While taking Auger data, after doing experiments continuously for a week or so, we noticed channel 1 showed zero counts. (Jan 30 2013)
• Red LED was dark at preamp and receiver for Chan 1, other channels normal
• verified CEM HV cable was connected.
• Opened preamp box, 7 modules, 1 per channel. No visible damage, nothing loose. 
• Tried to measure voltages by connecting preamp SHV connectors to Fluke 80K-40 high voltage probe (1 GOhm impedance) 1000:1 voltage divider with Fluke 179 multimeter, hemisphere at 100 V. 
• Got strange values, ~ 240-300 mV but not stable with time. 
• Expected ~ 1.5 V = 1500 V actual. 
• Channel 1 had only 3.4 mV
• With meter connected, channel indicated counts. All 7 similar.
• With multiplier off, swapped channels 1 & 6. preamp cables. Chan 1 still reports no counts, chan 6 OK. Problem not in UHV
• Swapped HV modules in "1127 Multiplier Supply". Problem moved with HV module
• HV module is defective
• Repair/exchange $750, in stock at Omicron US.
• New module installed 2/11/13, works

CEM Gain Adjust

Modified cover of multiplier supply so that the trimpots to set individual CEM voltages are accessible while the cover is closed. This makes CEM voltage adjustment safe and practical. Supply needs to be pulled halfway out of rack.

• Try to balance CEM signals. Pick flat part of spectrum, CAE mode. 
• Chan 2 is low, adjust to max gain. Adjust other channels to ~ match
• Increase supply knob setting to 9.00. No clear plateau in signal vs voltage

Auger imaging parameter optimization

- Sample: Au/Si, AS121130d
- Si peak Auger images were constructed using Auger maps measured at 1616.5, 1635, and 1650 eV.
- Auger maps were measured changing Path energy and Scan time.
- As shown in Fig. 1, optimal path energy for Auger imaging of Si is 160 eV (CRR mode, CAE[eV]/CAE=10).

                                       Fig. 1. Si 1616.5 eV Auger peak height at varying path energy.



- As shown in Fig. 2, as scan time increases, Auger image quality gets better. 21.6 min scan time is enough to get good quality images.

  Fig. 2. Si 1616.5 eV Auger peak height at varying scan time.

Path energy optimization for Nano-auger

- Sample: Si/Au AS121130d
- Auger spectra was measured on (100) Si region at varying Path energy.
- CRR mode from 320 eV to 80 eV
- CAE mode from 70 eV to 5 eV

                                        Fig. 1. Auger spectra measured on Si at varying path energy.

     Fig. 2. Si 1616.5 eV peak intensity vs. path energy and Si 1616.5 eV peak height vs. background ratio.