CIS OnCall and Troubleshooting
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No good solution is too small to go undocumented!!!
OnCall Responsibilities
CIS on-call share responsibilities for supporting the NP program goals.
Typical activities include ... * Pay attention to source operation and performance * Have a presence at daily discussion (7:45am and 8:00am) and weekly scheduling (1:30pm Wednesday) meetings * Participate in discussions, planning and testing of delivered beam performance e.g. transmission, stability, requirements or improvements
Greasing the R30 cable
A typical maintenance activity (every ~6 months) or whenever the HV cable is reinserted to the cermaic is to regrease the R30 cable/ceramic interface. * Lock-out the gun HVPS so high voltage cannot be generated on the cable. * Inspect the connection of cable to ceramic flange. It should be metal to metal. * Remove the cable flange screws holding it to the ceramic flange, and pull the cable upward, may feel stuck but requires good tug of 10-20 lbs of force to do so. * Use lint free cloth to wipe grease from the cable rubber plug, metal interface. Remove spring on banana plug spring, do the same and re-attach. That completes the cable cleaning. * Wrap some lint free cloth around forceps being careful there is no bare metal of forceps showing, and wet with toluene. Twist into ceramic and swirl moving upward to remove grease, repeat until fully clean. Do not leave toluene in ceramic as it will dissolve the new grease. This completes cleaning the ceramic. * Apply grease to cable rubber plug (not the metal at tip of cable or the spring) and smooth with gloved hand over the surface of the rubber plug. To gauge amount of grease start with about a 3" line from tube, and repeat as needed, typically a total of about 3 lines is sufficient. This completes the regreasing. * Insert the plug straight into the ceramic. For non-spring loaded cables set the initial gap between the cable flange and ceramic flange to about 5mm, then insert the screws and tighten down uniformly until the two flanges are metal to metal, ensuring good contact between the cable rubber plug and the ceramic surface. * Clean up, remove lock-out of HVPS, turn gun HV back on to verify OK.
Gun High Voltage Interlock Faults
* AC Line Volt Fault does not clear: you may want to recycle PSS system or reboot iocin3, see [1] for more details.
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
QE Measurement Script
It is useful for Operations or CIS staff to perform a daily measurement of photocathode QE using an automated script.
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)
Laser Related Issues
To change the laser pulsewidth ... * To start : PGun Main (John's laser control screen), then click Fiber Laser Super User, another screen appears. * From Fiber Laser Super User, click "Frequency Division Controls". Yes, this name no longer makes sense. It is now the screen to adjust the laser dc bias current. * From "Frequency Division Controls", adjust the dc bias current by following the instructions outlined by John Hansknecht, see link Media: laser seed drivr settings.pdf
Resetting LLRF quadrant detection : use with care ! * To start : JTABS => Tools Screen (right side of menubar) => Laser Quadrant Init Pulse (lower left related display) * Pick some diagnostic (separator viewer is best if setting phase of 250MHz rep rate e.g. invisible effect at chopper) * Choose laser A/B/C and cycled button from from 0=>1=>0 (i.e. leave at zero); repeat until phase is correct
Gun Current Monitoring
The gun current is calculated from the HVPS analog output that reports a voltage proportional to current output. We typically calibrated this HVPS output against beam well centered in PCUP (assumes no loss). The equation EPICS uses is a bit odd but Gun_Current = (HVPS - Offset)/Gain. The Offset is typically 0.15-0.25 V depending upon power supply and the Gain is typically 0.001 V/uA, i.e. ~1V/mA. Here are some examples with 150 kV Glassman supply from Feb 2016 and Jan 2011.