Beam Setup and Measurement - May 2018
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Beamline Survey and Elegant Optics Model
- September 2015 - Chris Tennant's Model copied here for reference /usr/opsdata/bubble/elegant/Sep2015
- May 2018 - Updated to include 2D spectrometer line and new harp IHA5D01 /usr/opsdata/bubble/elegant/May2018
- May 2018 Data Transmital media:DT_L1862.pdf
Operating the Cryounit at 4K
From past experience we have done a couple things...
- Communicate to the cryo coordinator before turning on SRF
- Generate a strip chart of liquid level, JT valve and the two unit gradients
- Adjust the gradients in small enough steps (~0.5) to allow recover equilibrium LL (JT will be larger w/ higher gradient)
Energy Setup and Measurement
- ...
Emittance Measurement
- Setup beam to FC2
- Use qsUtility configuration files to scan MQJ0L02 and/or MQJ0L02A and uses harp IHA0L03 -- files in default fileio directory for zig-zag dataCollector
/a/opsdata/fiefdata/fileio/q/qsUtility/config/F3-0/Bubble/ named IHA0L03_[x,y]_zigzag_bubble_2018_05_02_DAY.xml
- Be sure to enter the correct momentum in the configuration and/or analysis files
- Elegant optics lattice begins at MQJ0L02 (that is, use or propagate optics to that location)
Energy Spread Measurement
Setup beam to 2D spectrometer dump
- Upstream quads MQJ0L02 and MQJ0L02A can be any value but their integrated gradient value B'L (.BL field) must be recorded
- Use HarpFitterTool to scan IHA2D00 to measure horizontal beam size
Use Elegant to calculate the horizontal beta (betax) and the horizontal dispersion (etax) at the harp location
- Update lattice file
- Type command cd /usr/opsdata/bubble/elegant/May2018/lattice
- Edit lattice file BubbleChamber.lte
- Update K1 values for MQJ0L02/MQJ0L02A (they appear in only one place)
- Update energy spread elegant file
- Type command cd /usr/opsdata/bubble/elegant/May2018/energy_spread
- Edit command file energyspread.ele
- Update p_central_mev [MeV/c]
- Update beta_x [m] and beta_y [m] with qsUtility values computed at MQJ0L02
- Update emit_nx [m-rad] and emit_ny [m-rad] with qsUtility values compated at MQJ0L02
- Run Elegant model
- Type command cd /usr/opsdata/bubble/elegant/May2018/energy_spread
- Type command elegant energyspread.ele
- Type command sddsprintout -col=ElementName -col=betax -col=etax energyspread.twi
- Record value of betax [m] and etax [m] at IHA2D00
Set Beam Size at Radiator
Pre-requisite measurements
- Measured beam momentum in units of MeV/c
- Measured normalized emittance and Twiss parameters at MQJ0L02 (e.g. from qsUtility)
- Measured relative momentum spread (dp/p) (e.g. 1% is 0.01)
Define Elegant optimization (MQJ0L02, MQJ0L02A, MQD5D00, MQD5D01) to set beam size at radiator IDL5D01
- Update elegant optimization file with measured beam parameters
- Type command cd /usr/opsdata/bubble/elegant/May2018/beam_size
- Edit command file BubbleChamber_FIT.ele
- Update measured p_central_mev [MeV/c]
- Update measured beta_x [m] and beta_y [m] with qsUtility values computed at MQJ0L02
- Update measured emit_nx [m-rad] and emit_ny [m-rad] with qsUtility values compated at MQJ0L02
- Update measured relative momentum spread sigma_dp
- Update elegant optimization file with desired beam size and horizontal dispersion (there is no vertical dispersion)
- Update desired horizontal beam size by choosing a value of RMSX in this line: term="RADIATOR#1.Sx RMSX 1e-5 sene",
- Update desired vertical beam size by choosing a value of RMSY in this line: term="RADIATOR#1.Sx RMSY 1e-5 sene",
- Solution is normally calculated with zero dispersion at the radiator. IF this is not desired then comment (put ! in first column) following lines:
- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
- ! COMMENT (!) or UNCOMMENT FOR HORIZONTAL DISPERSION AT RADIATOR [m] (e.g. 0 is zero dispersion)
- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
- &optimization_term
- weight=1,
- term="RADIATOR#1.etax 0 1e-2 sene",
- verbose = 1,
- &end
Run Elegant Optimization
- Type command elegant BubbleChamber_FIT.ele
- Depending on difficulty of solution may take 20-30 min
- Terminal output will show result of optimization and desired quad values (in units of K1)
- You will need to convert from K1 to integrated field B'L (units of Gauss for EPICS .BL field)
- K1 [1/m^2] = 2.998 * B_EPICS [G] / (L [cm] * p [MeV/c]) ; note that L=15cm for both QJ and QD quads self-consistently
- Run also generates a new lattice named NEW.lte (where the quad values have been updated)
Generate final Elegant output of optimized solution
- Edit command file BubbleChamber.ele
- Update measured p_central_mev [MeV/c]
- Update measured beta_x [m] and beta_y [m] with qsUtility values computed at MQJ0L02
- Update measured emit_nx [m-rad] and emit_ny [m-rad] with qsUtility values compated at MQJ0L02
- Update measured relative momentum spread sigma_dp
- Type command elegant BubbleChamber.ele
Produce plots for comparison to viewer image and harp
- To view a 2D plot of the (x,y) distribution at one of the "watch" elements (ITV5D00, ITV5D01, IHA5D01) use correspond suffix e.g.,
- sddsplot -col=x,y -graph=dots BubbleChamber.TV5D01
- To print the numerical values of beam size at each element,
- sddsprintout -col=ElementName -col=s -col=Sx -col=Sy BubbleChamber.sig
- To make a scatter plot of RMS beam size,
- sddsplot -legend -graphic=line,vary BubbleChamber.sig -columnNames=s,'(Sx,Sy)'
- To make a projection plot of a watch file, say, watch.W1 .... first generate a histogram and then plot it, e.g.: (THANKS CHRIS!)
- sddshist watch.W1 W1.hist -dataColumn=x -bins=100 -lowerLimit=-5e-3 -upperLimit=5e-3 -normalize=area
- sddsplot -col=x,frequency -graph=lines W1.hist
- To make a plot of the optics:
- sddsplot -legend -graphic=line,vary BubbleChamber.twi -columnNames=s,'(betax,betay)' -yScalesGroup=id=beta -columnNames=s,'(alphax,alphay)' -yScalesGroup=id=alpha -columnNames=s,'(etax,etay)' -yScalesGroup=id=eta