CIS OnCall and Troubleshooting
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OnCall Responsibilities
CIS on-call share responsibilities for supporting the the user NP program goals.
Typical activities include ... * Pay attention to source operation and performance * Have a presence at daily 7:45am and 8:00am and weekly 1:30pm scheduling meetings * Monitor daily performance e.g. QE measurement, beam transmission, stability issues, etc.
250V Gun High Voltage FSD Comparator Faults
Use comparator circuit in ISB monitoring HVPS output to set window (range about +/- 500V) about gun high voltage. Faults can be real (gun HV is out of range) or false (comparator is drifting).
To check if the gun HV is actually drifting the following archived read backs are useful to view ... * Precision read back of Ross probe * HVPS lock set point * Horizontal orbit at IPM1I02
To determine if the gun HV window comparator is drifting or set incorrectly ... * Window drift during SAD can be found at startup * Window drift sensitive to temperature variation e.g. seasonal temperature swing * Window set too tightly by Ops
To set gun HV window comparator window ... * While clicking FSD clear button vary POT until resets to find a good region * High Limit : Increase POT while clicking until fault occurs, then decrease until fault clears and record new high value * Low Limit : Decrease POT while clicking until fault occurs, then increase until fault clears and record new low value * Set POT at center of new low and high values; maybe repeat to get consistent values
Diagnosing Beam Intensity and Position Noise
Use FastSEE BPM Mode to diagnose intensity and position from injector BPM's with 4 microsecond sampling
To start the fastSEE EPICS screen ... * To start : Accel Menubar => EDM => BPM => New FastSEE Control * MAC or Channel Access is required * Choose a BPM mode and BPM by selecting corresponding ioc e.g. iocse11
Notes for BPMSEE mode ... Non-invasive BPM spikes update correctly Less samples limit to lower frequency Make sure FastSee Light is ON
Notes for FastSEE mode ... Invasive BPM spikes update erratically More samples for higher frequency ~60kHz
Measuring and monitoring photocathode QE and charge lifetime
It is useful for Operations or CIS staff to perform a daily measurement of photocathode QE using an automated script. The photocathode charge lifetime is determined from a plot of QE measurement vs. charge delivered.
To configure and test QE Measurement Script ... * Determine laser attenuator values that generate same bunch charge from each laser e.g. in the 5-15 uA range * Load and save these values into the Injector Expert Script * Run QE measurement script selecting all lasers * Laser power and PCup current are measured for each laser in sequence * QE = (124 * I[uA]) / (P[mW]*Wavelength[nm)