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playground:alphatross [2020/03/17 16:30] jacobs |
playground:alphatross [2020/06/16 15:52] carter |
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==== NEC Alphatross RF Source Instructions ==== | ==== NEC Alphatross RF Source Instructions ==== | ||
- | THESE ARE DRAFT INSTRUCTIONS WRITTEN REMOTELY. THERE MAY BE OMISSIONS AND INCORRECT NOMENCLATURE, USE YOUR OWN JUDGEMENT... | ||
- | |||
** __START UP__ ** | ** __START UP__ ** | ||
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- Monitor the Ion Gauge pressure, it should remain less than 4 x 10-6 Torr while setting the Probe. It should settle to around 2 x 10-6 or less when done. | - Monitor the Ion Gauge pressure, it should remain less than 4 x 10-6 Torr while setting the Probe. It should settle to around 2 x 10-6 or less when done. | ||
- Raise the Probe Voltage to 3 KV as a start, this might be enough to get the plasma going. | - Raise the Probe Voltage to 3 KV as a start, this might be enough to get the plasma going. | ||
- | - If there is still no plasma try raising the Mass Flow setting to as much as .5 SCCM to inspire ignition and then return to .35 SCCM. | + | - If there is still no plasma try raising the Mass Flow setting to as much as 0.5 SCCM to inspire ignition and then return to 0.35 SCCM. |
+ | - **This is a pause point for source clean up, can run like this for days, should reduce probe current over time** | ||
- Monitor the Probe Current, maintain 3 mA +/- 1 mA, and continue raising the Probe Voltage until it reaches 6.5 KV. | - Monitor the Probe Current, maintain 3 mA +/- 1 mA, and continue raising the Probe Voltage until it reaches 6.5 KV. | ||
- Set the Oven Voltage to 87 V, wait ten minutes. After 10 minutes the Oven Temp should be around 150 C. | - Set the Oven Voltage to 87 V, wait ten minutes. After 10 minutes the Oven Temp should be around 150 C. | ||
- Set the Extractor Voltage to 5.5 KV and the Bias Voltage to a value that gives the desired injection energy less (6.5 + 5.5). Beam yield seems to increase with injection energy above 30 KeV. Suggest trying 41 or 53 KeV settings if pulsing. | - Set the Extractor Voltage to 5.5 KV and the Bias Voltage to a value that gives the desired injection energy less (6.5 + 5.5). Beam yield seems to increase with injection energy above 30 KeV. Suggest trying 41 or 53 KeV settings if pulsing. | ||
- You may now be able to look at negative beam in the source faraday cup (#7 on the FC meter). Its not clear if this is a useful endeavor. | - You may now be able to look at negative beam in the source faraday cup (#7 on the FC meter). Its not clear if this is a useful endeavor. | ||
- | - Beam yield will increase as Mass Flow is reduced, expect optimum yield at //around// .2 SCCM. | + | - Beam yield will increase as Mass Flow is reduced, expect optimum yield at //around// 0.2 SCCM. |
- Optimize negative beam yield by tuning Extractor Voltage, Focus Voltage, and Mass Flow. Adjust Bis Voltage accordingly if an exact injection energy is required for P&B. Expect little or no Focus Voltage. | - Optimize negative beam yield by tuning Extractor Voltage, Focus Voltage, and Mass Flow. Adjust Bis Voltage accordingly if an exact injection energy is required for P&B. Expect little or no Focus Voltage. | ||
- Use software buttons to take out faraday cup and open gate valve. | - Use software buttons to take out faraday cup and open gate valve. |