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tuning_the_s800_xdt [2015/10/26 13:57] pereira [Checking Particle ID and rate at S800 FP] |
tuning_the_s800_xdt [2015/10/26 14:08] pereira [Reaction Setting] |
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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) ==== | ==== Analysis line classic PPAC setup (Focus optics only) ==== | ||
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* " | * " | ||
* Classic PPACs have rate limitations from pileups | * Classic PPACs have rate limitations from pileups | ||
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* 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. | * 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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- | ==== Setup beamline ==== | ||
- | * Object and XF scintillators and intermediate image PPACs inserted if they will be used | ||
- | * If Object scintillator will not be used, there is no reason to look at beam on it unless to debug a problem with the transmission | ||
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- | * Set spectrograph Brho for unreacted fragment | ||
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- | ==== Start scalers ==== | ||
- | * Use s800 account | ||
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- | * Make sure experiment daq is: | ||
- | * Stopped | ||
- | * Gone | ||
- | * Open terminal window (from bottom of mac) | ||
- | * ssh to spdaq20 | ||
- | * ps auw | grep Readout | ||
- | * Does not get restarted | ||
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- | * Under operations folder on mac | ||
- | * scalers (gives error if no bridge) | ||
==== Setting Optimization ==== | ==== Setting Optimization ==== | ||
=== Focused optics === | === Focused optics === | ||
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* Expectations for A1900 FP to S800 FP transmission | * Expectations for A1900 FP to S800 FP transmission | ||
* 80% or better for mid-Z fragments | * 80% or better for mid-Z fragments | ||
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- | === Matched optics === | ||
- | * Typically much more time is invested for optimizing optics for matched optics than for focused optics | ||
- | * One input is optimizing for transmission | ||
- | * For tritons a scintillator is required at the pivot position since fragments at 5 Tm will not reach S800 FP | ||
- | * The last two analysis line triplets are used to tweak for the desired optical properties | + | ==== Coincidences |
- | + | ||
- | * Document optimized transmission with another run to disk to measure rate of fragment of interest at S800 FP | + | |
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- | ===== Reaction Setting | + | |
- | + | ||
- | ==== Setting up Reaction Settings ==== | + | |
- | * 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, if necessary | ||
- | * 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 | ||
- | * A graphic tool is available to help (not yet calibrated) | ||
- | * 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 ==== | ||
* Overview | * 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. | * 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. | ||
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====== Dispersion Matching tuning ====== | ====== Dispersion Matching tuning ====== | ||
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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, | 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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* 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 | * 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 | ||
+ | |||
+ | |||
+ | * Reaction setting to FP | ||
+ | * Start with Attenuator setting of unreacted beam and step up in intensity | ||
+ | * Set up beam blocker, if necessary | ||
+ | * 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 | ||
+ | * A graphic tool is available to help (not yet calibrated) | ||
+ | * 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 | ||