tuning_the_s800_xdt
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tuning_the_s800_xdt [2015/10/26 13:59] pereira [Checking Particle ID and rate at S800 FP] |
tuning_the_s800_xdt [2015/10/27 14:20] pereira [Setting up Reaction Settings] |
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| * Adjust MCFD threshold: | * Adjust MCFD threshold: | ||
| - | * Open configuration file **MCFD16.tcl** in **/user/s800/ | + | * Using the [[s800 daq tools# |
| * The OBJ signal feeding this module is not patched out to data U6 | * The OBJ signal feeding this module is not patched out to data U6 | ||
| - | * The OBJ signal from MCFD-16 module goes to the Mesytec | + | * The OBJ signal from MCFD module goes to the Mesytec |
| * Make sure that the threshold of the XFP MCFD channel is reasonable. Rates in scaler channels XFP.Scint and XFP.MCFD.Scint should be comparable | * Make sure that the threshold of the XFP MCFD channel is reasonable. Rates in scaler channels XFP.Scint and XFP.MCFD.Scint should be comparable | ||
| * Adjust MCFD OBJ threshold looking at scalers. The ratio of OBJ to XFP scaler rates (channels OBJ.MCFD.Scint and XFP.MCFD.Scint) should reflect the transmission of the cocktail beam | * Adjust MCFD OBJ threshold looking at scalers. The ratio of OBJ to XFP scaler rates (channels OBJ.MCFD.Scint and XFP.MCFD.Scint) should reflect the transmission of the cocktail beam | ||
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| * Adjust the TDC delays of E1 up, down using the Delay GUI | * Adjust the TDC delays of E1 up, down using the Delay GUI | ||
| * In principle, the TACs delays don't need to be adjusted | * In principle, the TACs delays don't need to be adjusted | ||
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| ==== Checking Particle ID and rate at S800 FP ==== | ==== Checking Particle ID and rate at S800 FP ==== | ||
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| * Take a run on disk | * Take a run on disk | ||
| * Measure the beam intensity again and calculate the average value | * Measure the beam intensity again and calculate the average value | ||
| - | * In **[[s800 SpecTcl|SpecTcl GUI]], click **Attach to File** and select data file **run-xxxx-xx.evt** in directory **/ | + | * In [[s800 SpecTcl|SpecTcl GUI]], click **Attach to File** and select data file **run-xxxx-xx.evt** in directory **/ |
| * Check the run time and live time from the corresponding scaler file in directory **/ | * Check the run time and live time from the corresponding scaler file in directory **/ | ||
| * Calculate the rate and purity and compare with the value in the A1900 FP to determine the transmission | * Calculate the rate and purity and compare with the value in the A1900 FP to determine the transmission | ||
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| + | ==== Analysis line classic PPAC setup (Focus optics only) ==== | ||
| + | **THIS SECTION IS STILL IN PROGRESS** | ||
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| + | * " | ||
| + | * Classic PPACs have rate limitations from pileups | ||
| + | * TPPACs are not as efficient as CRDCs for low Z because it is not currently setup to set thresholds on individual pad readouts | ||
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| + | * Checking PPACs with beam | ||
| + | * Scalers do not provide reliable diagnostic information because of noise | ||
| + | * Bias PPACs while looking at patched out anode signal on scope to check for sparking | ||
| + | * Typical starting value: 400V | ||
| + | * A sample HV sample for < | ||
| + | * Look at spectra of raw up, down, left, right, anode to decide on bias | ||
| + | * Run with smaller p-acceptance (e.g., 0.5%) | ||
| + | * Efficiency against Focal plane CRDCs should be 100% | ||
| + | * Optimize bias setting based on raw signals | ||
| + | * Check that position spectra look reasonable | ||
| + | * Run with larger p-acceptance (e.g., 2%) | ||
| + | * Efficiency against Focal plane CRDCs should be 100% | ||
| + | * Record run showing tracking | ||
| + | * Confirm angular dispersion: ~50 mrad/% (not an absolute measurement) | ||
| + | * Confirm correlations between dispersive angle at intermediate image and p in FP (e.g., crdc1x). This correlation will be somewhat washed out by straggling in the target; in principle, this should be checked without the target, but the benefit vs. cost in time to remove the target is not worth it. | ||
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| + | ==== Setting Optimization ==== | ||
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| + | * Expectations for A1900 FP to S800 FP transmission | ||
| + | * 80% or better for mid-Z fragments | ||
| + | * >60% for low-Z fragments with large angles | ||
| + | * 40% transmission might be a cause for concern for high-Z beam with charge state losses in detectors/ | ||
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| + | * Strategy for optimizing transmission | ||
| + | * Want to balance losses between S800 analysis line and Transfer Hall (the S800 analysis line is typically slightly worse) | ||
| + | * Best diagnostic is scalers from S800 FP, object scintillator and XF scintillator | ||
| + | * Using the knob box and the NCS application **QtKM** (file **BLSetup_A1900.gkm**), | ||
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| + | * Document optimized transmission with another run to disk to measure rate of fragment of interest at S800 FP | ||
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| + | ====== Dispersion Matching Mode ====== | ||
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| + | In the dispersion-matching optics, the S800 focal point is achromatic, i.e. the position of the beam in the dispersive direction does not depend on the momentum. As a consequence, | ||
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| + | Charge-exchange experiments require typically this optics. In some cases, the beam used is < | ||
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| + | * Set trigger to “s800 trigger” | ||
| + | * Ensure that the **[[s800 daq tools# | ||
| + | * Under trigger tab select **s800 trigger** (which is E1 up by definition) | ||
| + | * Deselect experiment trigger | ||
| + | * SAVE TO FILE | ||
| + | * Stop and start **[[s800 daq tools#Run Control Window|RunControl]]** to assert new trigger condition | ||
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| + | * Select **[[s800 SpecTcl|Spectcl]]** window **S800_DISPMATCH.win** | ||
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| + | * We need to start checking the spectra showing the correlations between angle and position in both dispersive and non-dispersive directions. We typically use the spectrum **CRDC1.XG_CRDC1.TAC** for the non-dispersive direction, and **S800.FP.TRACK.XFP_TRACK.AFP** for the dispersive direction | ||
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| + | * The parabolas seen in the above spectra correspond to reactions with H in the target. The blurred lines on the right of the parabolas correspond to reaction with C. It is hard to see clearly this lines, so we need to make several gates | ||
| + | * Open spectrum **E1.DE_TOF.RF** and define a gate around < | ||
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| + | * This gate is used to fill spectra **S800.FP.TRACK.XFP_TRACK.AFP!FOI** and **CRDC1.XG_CRDC1.TAC!FOI**. As can be seen in the figures below, this gate " | ||
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| + | * Define rectangular gates in this spectra, making sure that it is narrow enough to select a vertical section of the parabolas, but wide enough to get enough statistics. Call them **afp** (in spectrum **CRDC1.XG_CRDC1.TAC!FOI**) and **bfp** (in spectrum **S800.FP.TRACK.XFP_TRACK.AFP!FOI**). After applying these new gates, the kinematics spectra are very clean | ||
| + | {{: | ||
| + | * The pre-defined gate **allgates** is made by the AND condition of all the gates defined above (**foi**, **afp**, and **bfp**). This gate is used to fill the spectrum **CRDC1.XG!FOI-AFP-BFP**, | ||
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| + | * The leftmost peak corresponds to reactions with H. The central peak are reaction with C. The goal of the tweak is to make these peaks as narrow as possible | ||
| + | * Open the NCS application **QtKM** in the Applications Menu. Open file **BLSetup_A1900.gkm**. The magnetic elements that are typically tweaked with the knob box sitting on the left side of u6pc5 are **I232TA**, **I236TC**, and **I245TC** which can be found on page **S800 BLine+Spectrograph**. Other elements used to improve the focusing in the object point, and the transmission are **I172QA** and **I174QB**. The goal of the dispersion-matching tuning is to find a compromise between transmission and resolution. | ||
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| + | * The two figures below show the spectrum **CRDC1.XG!FOI-AFP-BFP** before (top) and after (bottom) the dispersion-matching tuning for a typical experiment. Be aware that the width given by SpecTcl for the selected peak is not too reliable. It is more convenient to do a real gaussian fit. Unfortunatelly this is not an option included in the current version of SpecTcl. That's why some device physicists prefer SpecTk for this type of tuning | ||
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| + | ====== Reaction Setting ====== | ||
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| + | ===== Setting up Reaction Settings ====== | ||
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| + | * Calculating reaction setting | ||
| + | * Center unreacted beam at S800 FP | ||
| + | * Adjust spectrograph Brho to center beam at S800 FP | ||
| + | * Requirements for a beam to be “Centered” | ||
| + | * Spectrograph dipoles matched | ||
| + | * Beam position within about 1 cm of center as judges by 0 point on crdc1x spectrum or on track.xfp spectrum | ||
| + | * Record run to disk to document centered unreacted beam setting | ||
| + | * Calculate reaction setting using “effective” beam energy and the nominal target thickness | ||
| + | * Ideally, experimenters should be the ones making this calculation | ||
| + | * This approach assumes that the target thickness is known | ||
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| + | * Reaction setting to FP | ||
| + | * Start with Attenuator setting of unreacted beam and step up in intensity | ||
| + | * Set up beam blocker (labeled I255 Slits) in the S3 page of Barney, if necessary | ||
| + | * Expected " | ||
| + | * Expect to see unreacted beam if reaction setting is within +/- 3% of unreacted beam setting | ||
| + | * Should have to move only one of the two blockers unless charge states are present | ||
| + | * Try to cut only as much as necessary; depends on | ||
| + | * What rate limits allow | ||
| + | * What experimenters want (e.g., if they want singles, the cut has to be more restrictive to limit acquisition deadtime) | ||
| + | * Move blocker, decrease attenuator, repeat | ||
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| + | ===== Coincidences ===== | ||
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| + | * Overview | ||
| + | * Most experiments at the S800 involve setting up an auxiliary detector system (e.g. SeGA, HiRA, etc) to be used in coincidence with the standard detectors of the S800. | ||
| + | * The auxiliary detector provides a secondary trigger that is fed into the S800 trigger system | ||
| + | * A key part of setting up the S800 for such experiments is getting proper timing setup between the S800 and any auxiliary detectors | ||
| + | * For cases where the Secondary detector has a slow response relative to the S800, the coincidence timing must be reset to the S800 timing by delaying the S800 trigger using the third gate and delay generator on the trigger GUI | ||
| + | * A typical S800 delay for SeGA is 450 ns | ||
| + | * Probably smaller typical S800 delay needed for HiRA | ||
| + | * An example of experiments where auxiliary detectors are not used and, thus, setting up coincidence timing is not an issue are the experiments with tritons run by the charge exchange group | ||
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| + | * Choice of setting to be used for coincidence timing setup | ||
| + | * The reaction of interest for the experiment can be used to setup coincidences only if the rate of coincidences is high enough | ||
| + | * Sometime the pilot beam is used for setting up the coincidence timing in cases where the intensity of the secondary beam is too small | ||
| + | * Example: | ||
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| + | * Setup | ||
| + | * Coincidence signals are usually visible on scope without running scope in acquire mode | ||
| + | * Adjust the width of the early signal (S800 or secondary) should be wide enough to catch coincidences with the late signal (width of late signal is not critical) | ||
| + | * Readjust TDC delays based on changes made to S800 trigger delay | ||
| + | * Experimenters will need to adjust their delays based on delay made to S800 trigger | ||
| + | * Have experimenters record a run with coincidences on their account | ||
| + | * S800 trigger TDC channel should show a peak (which corresponds to coincidences) | ||
| + | * " | ||
| + | * This check is required for verification in cases of low beam intensity (e.g. 1000 pps) | ||
| + | * Length of run required is typically about 10-15 minutes | ||
| + | * To be resolved: | ||
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| + | * Sample timing for running S800 with SeGA | ||
| + | * SeGA trigger is late with respect to S800 trigger | ||
| + | * The figure below represents a timing schematic to show how to | ||
| + | * Setup of the S800 trigger to recover timing needed for proper functioning of S800 FP detectors | ||
| + | * Set up the coincidence trigger | ||
| + | * See: http:// | ||
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| + | {{: | ||
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| + | * A double peak structure will appear in the TDC for the S800 trigger between the coincidence events and the singles events (see figure below); the groups are separated by 25 ns because of the delay introduced by the downscaler used for the singles | ||
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| + | ====== Follow-up ====== | ||
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| + | * Before leaving beam with experimenters | ||
| + | * Set up current trip points on Linux HV controls | ||
| + | * Values used for K-48 | ||
| + | * 5 for CRDC and Ion Chamber anodes and intermediate image ppacs | ||
| + | * 50 for CRDC drifts | ||
| + | * 80 for IC drift | ||
| + | * Ensure alarms are running | ||
| + | * Make sure Linux HV GUI alarms are enabled | ||
| + | * Make sure threshold on isobutane level is set up (not currently connected to alarms because they give too many false alarms when communication is lost) | ||
| + | * All logs are being recorded | ||
| + | * There is no log file for biases controlled by Labview | ||
| + | * Linux HV | ||
| + | * LabView gas handling system | ||
| + | * Note in logbook | ||
| + | * Scintillator biases | ||
| + | * IC gate biases | ||
| + | * Post reference printouts for experimenters | ||
| + | * HV status: a snapshot of HV GUI | ||
| + | * Gas handling system status: a snapshot of LabView window | ||
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| + | * Create window configuration with summing regions to make it easier for experimenters to track efficiency/ | ||
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| + | * Setting up coincidences for additional reaction settings in an experiment | ||
| + | * Do not need to redo coincidence settup if secondary beam does not change | ||
| + | * Might need to redo coincidence setup if secondary beam changes drastically | ||
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| + | * To watch during experiment | ||
| + | * Look for isobutene running out – messes up data over several hours | ||
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| + | * Implementing dE- or TOF-based corrections is part of EXR | ||
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| + | More detail needed | ||
| + | Minimum rates required for coincidence setup | ||
| + | Selection of appropriate substitute reactions for coincidence setup | ||
| + | How to feel comfortable that there will not be a problem with FP detector gases running out | ||
| + | Starting alarms | ||
| + | Starting logging | ||
tuning_the_s800_xdt.txt · Last modified: 2023/09/22 15:15 by swartzj
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