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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 [2023/09/22 14:51] swartzj [CRDCs setup] |
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* Ensure that the S800 spectrograph magnets are tuned to the right rigidity | * Ensure that the S800 spectrograph magnets are tuned to the right rigidity | ||
- | * Verify that the beam blocker | + | * Verify that the FP beam blocker is fully open: |
- | * Expected " | + | |
- | + | ||
- | * Ensure that CRAD04 (typically connected to object scintillator) is enabled with a rate limit of **20 kHz** (CRAD04 looks at E1 up FP scintillator) | + | |
* Remember: S800 FP rate limit is **6 kHz** | * Remember: S800 FP rate limit is **6 kHz** | ||
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* For U-238 (88+) @ ~70 MeV/u: UP (1180 V); DOWN (1280 V) | * For U-238 (88+) @ ~70 MeV/u: UP (1180 V); DOWN (1280 V) | ||
- | * Have a good expectation of rate from A1900 group information or from timing scintillators (typically | + | * Have a good expectation of rate from ARIS group information or from timing scintillators (typically |
- | * Remove stops to look for beam at S800 FP with **[[s800 daq tools# | + | * Remove stops to look for beam at S800 FP with **[[s800 daq tools# |
* Look at FP scintillator scalers (E1 up, E1 down) | * Look at FP scintillator scalers (E1 up, E1 down) | ||
* There are typically a few scaler counts without beam | * There are typically a few scaler counts without beam | ||
+ | * If needed, adjust beam rate with operators | ||
+ | |||
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* Bias detector. Typical bias: **1200-1800 V** (up to 2200 V) | * Bias detector. Typical bias: **1200-1800 V** (up to 2200 V) | ||
- | * Use **[[electronics overview|scope]]** | + | * Use oscilloscope |
- | * This signal is sent to the CANBERRA 454 Quad CFD in data U6 | + | * Check rise time and amplitude. Good signal: ~10 ns rise time; 400-500 mV amplitude |
- | * One of the output from this CFD is sent (via patch panel #62) to the TAC and scaler (channel OBJ.Scint) in S3. The other output goes through a passive delayed, and is sent (via patch panel #67) to the Phillips TDC | + | * Check if there are reflections (typically seen at ~300 ns after main peak) |
- | * Check raising | + | |
- | * Using the scope, check the CFD setting: | + | |
- | * Check CFD walk inspect signal in scope by triggering scope with CFD output | + | * Check [[s800 daq tools# |
+ | * Trigger oscilloscope with MCFD output (see labels in patch panel), and plug analog signal | ||
+ | * Verify that MCFD delay is ok | ||
+ | * Adjust MCFD gain based on signal amplitude | ||
+ | * Adjust threshold to minimize noise | ||
+ | * Check if MCFD output displays signals triggered by reflections (~300 ns following main peak). If that is the case, increase thresholds or signal width (this is valid only for low-rate experiments) | ||
+ | * Measure OBJ in scalers and compare it with DB5. Does it make sense? | ||
+ | * Stop beam and verify background (it should be minimum) | ||
+ | |||
+ | | ||
+ | * Check CFD walk: inspect signal in scope by triggering scope with CFD output | ||
* Ensure that CFD delay cable is ok: about 80% of raising time of the input signal | * Ensure that CFD delay cable is ok: about 80% of raising time of the input signal | ||
- | * Adjust | + | * Trigger oscilloscope with CFD output, and check analog signals |
+ | * Adjust | ||
+ | * Check if CFD output displays signals triggered by reflections (~300 ns following main peak). If that is the case, increase thresholds or signal width (this is valid only for low-rate experiments) | ||
+ | * Measure OBJ in scalers | ||
+ | * Stop beam and verify background (it should be minimum) | ||
+ | |||
+ | |||
+ | * NOTE: | ||
+ | * Be aware that sometimes, after running for a while, the OBJ box is activated. This results in a non-negligible count rate in OBJ scalers with beam off, which comes from HIGH amplitude signals (not noise). DO NOT try to eliminate this " | ||
+ | * The ratio of OBJ to ARIS (DB5) scaler rates (channels OBJ.Scint and XFP.Scint) should reflect the transmission of the cocktail beam (between 60% to 90%, depending on quality of tunning) | ||
- | * Adjust MCFD threshold: | ||
- | * Open configuration file **MCFD16.tcl** in **/ | ||
- | * The OBJ signal feeding this module is not patched out to data U6 | ||
- | * The OBJ signal from MCFD-16 module goes to the Mesytec MTDC32 module and scaler (channel OBJ.MCFD.Scint) | ||
- | * 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 | ||
- | * Save new threshold in configuration file **MCFD16.tcl** | ||
- | |||
- | * Watch for no rate change on scaler display with a bias adjustment up or down of about 50-100 V | ||
==== FP scintillator setup ==== | ==== FP scintillator setup ==== | ||
+ | |||
+ | * Make sure that S800 DAQ is in [[s800 daq tools# | ||
* Set trigger to “s800 trigger” | * Set trigger to “s800 trigger” | ||
- | * Ensure that the **[[s800 daq tools# | + | * Ensure that the **[[s800 daq tools# |
* Under trigger tab select **s800 trigger** (which is E1 up by definition) | * Under trigger tab select **s800 trigger** (which is E1 up by definition) | ||
* Deselect experiment trigger | * Deselect experiment trigger | ||
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* End and Begin **[[s800 daq tools#Run Control Window|ReadoutGUI]]** to assert new trigger condition | * End and Begin **[[s800 daq tools#Run Control Window|ReadoutGUI]]** to assert new trigger condition | ||
- | * Select **[[s800 SpecTcl|Spectcl]]** window **S800_SCINT.win** | + | * Select **[[s800 SpecTcl|Spectcl]]** window **S800_SCINT.win** |
* Adjust **[[hv bias|bias]]** looking at 2D spectra **e1.deup_e1.dedown** (showing the parameters s800.fp.e1.de_down vs. s800.fp.e1.de_up) for the FP E1 scintillator | * Adjust **[[hv bias|bias]]** looking at 2D spectra **e1.deup_e1.dedown** (showing the parameters s800.fp.e1.de_down vs. s800.fp.e1.de_up) for the FP E1 scintillator | ||
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* Adjust biases so that unreacted beam are at 1/3 to 1/4 of dynamic range | * Adjust biases so that unreacted beam are at 1/3 to 1/4 of dynamic range | ||
* Reaction product will typically be similar enough to unreacted beam particles | * Reaction product will typically be similar enough to unreacted beam particles | ||
- | * Different particles with different energy | + | * Different particles with different energy |
| | ||
{{: | {{: | ||
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- | * Select **[[s800 SpecTcl|Spectcl]]** window **S800_IC.win** | + | * Select **[[s800 SpecTcl|Spectcl]]** window **S800_IC.win** |
* Adjust pad gains | * Adjust pad gains | ||
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{{: | {{: | ||
- | * Gains are controlled in **s800shpini.tcl** file in directory **s800/operations/daq/usb/Configs** (an example of the content of this file can be seen {{: | + | * Gains are controlled in **s800shpini.tcl** file in directory **/user/s800/s800daq/Configurations** (an example of the content of this file can be seen {{: |
* First shaper is for ion chamber | * First shaper is for ion chamber | ||
* Typically, only coarse gains are used | * Typically, only coarse gains are used | ||
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* **[[hv bias#hv remote control|Bias]]** CRDCs | * **[[hv bias#hv remote control|Bias]]** CRDCs | ||
* Look at anode signal on **[[electronics overview|scope]]** | * Look at anode signal on **[[electronics overview|scope]]** | ||
- | * Patched to data-U6 on labeled connector | + | * Patched to data-U4 on labeled connector |
* **200 – 500 mV** signals are good | * **200 – 500 mV** signals are good | ||
* CRDC1 anode is noisier (digital noise) than CRDC2 | * CRDC1 anode is noisier (digital noise) than CRDC2 | ||
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* Count rate is a little higher than on scintillator due to noise or thresholds | * Count rate is a little higher than on scintillator due to noise or thresholds | ||
- | * Check **[[s800 SpecTcl|Spectcl]]** window **S800_CRDCS.win** (see figure below) to verify the good performance of the detectors. (The spectra for each CRDC can be checked | + | * Check **[[s800 SpecTcl|Spectcl]]** window **S800_CRDCS.win** (see figure below), or, alternatively **S800_MEGASUMMARY.win** |
- | * Spectra **crdc1.raws** and **crdc2.raws** | + | * Spectra **crdc1.raws** and **crdc2.raws** |
- | * Each spectra | + | * Each spectrum |
* The 224 pads are assembled along the dispersive direction | * The 224 pads are assembled along the dispersive direction | ||
* Width of beam peak is proportional to A1900 p-acceptance in focus optics | * Width of beam peak is proportional to A1900 p-acceptance in focus optics | ||
* Width is narrower in match optics | * Width is narrower in match optics | ||
* Adjust anode HV to bring fuzzy maximum to around 600-700 channels (saturation of each pad at ~ 1000 ch) | * Adjust anode HV to bring fuzzy maximum to around 600-700 channels (saturation of each pad at ~ 1000 ch) | ||
+ | * These are good spectra to check if the pad thresholds are properly set. Thresholds are too low if you see that all pads are firing at low energies. If that's the case, increase the pad thresholds in files **s800crdcv1.tcl** and **s800crdcv2.tcl**, | ||
- | * Spectra **crdc1.anode_crdc1.tac** and **crdc2.anode_crdc2.tac** | + | * Spectra **crdc1.anode_crdc1.tac** and **crdc2.anode_crdc2.tac** |
* This spectrum is used to ensure that the field in the detectors is uniform and well aligned. If the detector is working properly, then the amplitude of the ANODE signals should not depend on the position of the beam (as shown in the figure below) | * This spectrum is used to ensure that the field in the detectors is uniform and well aligned. If the detector is working properly, then the amplitude of the ANODE signals should not depend on the position of the beam (as shown in the figure below) | ||
* If the field is not well aligned, then there will be a correlation between ANODE signals and TAC signals | * If the field is not well aligned, then there will be a correlation between ANODE signals and TAC signals | ||
- | * Spectra **crdc1.x_crdc1.padsum** and **crdc2.x_crdc2.padsum** | + | * Spectra **crdc1.x_crdc1.padsum** and **crdc2.x_crdc2.padsum** |
* It shows the sum over multiple sampled signals from each pad along the (dispersive) x position | * It shows the sum over multiple sampled signals from each pad along the (dispersive) x position | ||
* The padsum signals should not show any correlation with the x (dispersive) position | * The padsum signals should not show any correlation with the x (dispersive) position | ||
- | * Spectra **crdc1.xg_crdc1.tac** and **crdc2.xg_crdc2.tac** | + | * Spectra **crdc1.xg_crdc1.tac** and **crdc2.xg_crdc2.tac** |
* It shows the beam distribution in the dispersive (xg) //vs// non-dispersive (tac) directions | * It shows the beam distribution in the dispersive (xg) //vs// non-dispersive (tac) directions | ||
* It is used to ensure that the fragment beam is centered in the detectors | * It is used to ensure that the fragment beam is centered in the detectors | ||
* It is also used to see the effect of the beam blocker (used to stop intense contaminants) in the cocktail beam | * It is also used to see the effect of the beam blocker (used to stop intense contaminants) in the cocktail beam | ||
| | ||
- | * Spectra **crdc1.xg** and **crdc2.xg** | + | * Spectra **crdc1.xg** and **crdc2.xg** |
* It shows the position of the beam in the dispersive direction, evaluated by calculating the " | * It shows the position of the beam in the dispersive direction, evaluated by calculating the " | ||
- | + | | |
- | | + | |
* They correspond to the non-dispersive position of the beam in the CRDCs. | * They correspond to the non-dispersive position of the beam in the CRDCs. | ||
- | {{: | + | * Spectra **crdc1.pad_mult** and **crdc2.pad_mult** |
+ | * They show the distribution of pad multiplicities (i.e. number of pads firing for each event). Typical average values are ~10-15. Significantly larger average multiplicities might indicate that the thresholds are set too low. | ||
+ | |||
+ | {{: | ||
+ | |||
+ | |||
+ | * Check **[[s800 SpecTcl|Spectcl]]** window **S800_CRDCS_EFF.win** (see figure below) to verify the efficiency of the detectors. | ||
+ | * Start a new run recording data on disk | ||
+ | * Make a gate in spectrum **ic.sum** (top right plot) to select the Z region of interest, and call it **ic** | ||
+ | * Make a summing region around the " | ||
+ | * Stop the run and rescan data from disk | ||
+ | * Compare the number of event inside the 2D summing regions with the number of events inside the **ic** gate. Typically the former are very close to the later (nearly 100% efficiency for medium/high Z) | ||
+ | {{: | ||
==== Timing setup ==== | ==== Timing setup ==== | ||
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* Select SpecTcl window **S800_TOF.win** | * Select SpecTcl window **S800_TOF.win** | ||
- | * The three columns correspond to the **RF-FP** ToF (left), **OBJ-FP** (center), and **XFP-FP** (right) | + | * The three columns correspond to the **RF-FP** ToF (left), **OBJ-FP** (center), and **XFP-FP** (right). |
- | * The first (top) row corresponds to the Phillips TDC | + | * The first (top) row corresponds to the Phillips TDC. |
- | * The second row corresponds to the MTDC with all the hits included | + | * The second row corresponds to the MTDC with all the hits included. Note that in a unreacted-beam setting, the first hit typically provides the " |
- | * The third row corresponds to the MTDC with only the first hit | + | * The third row corresponds to the MTDC with only the first hit. |
- | * The fourth row corresponds to the ORTEC TACs. Note that there is not **RF-FP TAC** | + | * The fourth row corresponds to the ORTEC TACs. Note that there is not **RF-FP TAC**. |
- | * The two spectra in the fifth row corresponds | + | * The two spectra in the fifth row correspond |
* An empty ToF spectrum means that either the delays are not right (and need to be adjusted) or the spectrum range is too narrow | * An empty ToF spectrum means that either the delays are not right (and need to be adjusted) or the spectrum range is too narrow | ||
- | * The MTDC spectra | + | * The MTDC delays |
{{: | {{: | ||
- | * If necessary, adjust delays: | + | |
- | * Using the [[S800 DAQ tools# | + | * Use the spectra **TOF.MTDC_RF**, |
- | * Select | + | * Using the cursor mouse, check the lower and higher limits defining the region in the MTDC ToF spectra with the " |
- | * Adjust the TDC delays of OBJ and XFP using the delay boxes connected to the CANBERRA CFD 454 in data U6 | + | * Go to the **Variables** page in SpecTcl GUI and assign the limits to the following variables: |
- | * Adjust | + | * **s800.fp.vmetdc.mtdc_rflow** and **s800.fp.vmetdc.mtdc_rfhigh** for RF-XFP |
- | * In principle, the TACs delays don't need to be adjusted | + | * **s800.fp.vmetdc.mtdc_objlow** and **s800.fp.vmetdc.mtdc_objhigh** for OBJ-XFP |
+ | * **s800.fp.vmetdc.mtdc_xfplow** and **s800.fp.vmetdc.mtdc_xfphigh** for XFP-XFP | ||
+ | * For each ToF, SpecTcl will search the hit number that fits in the selected region. The new MTDC ToF parameters are **s800.fp.vmetdc.mtdc_rf**, | ||
+ | |||
+ | | ||
+ | * Using the [[S800 DAQ tools# | ||
+ | * Connect | ||
+ | * Adjust the TDC delays of OBJ and/or XFP with respect to the TDC start using the delay boxes connected to the CANBERRA CFD 454 in data U6 (~200 ns delay is good) | ||
+ | * Check the corresponding ToF spectra in SpecTcl to confirm that the timings are properly adjusted. | ||
+ | |||
+ | * Check the efficiencies | ||
+ | * Make a gate on spectrum **IC.SUM** selecting the region of interest, and call it " | ||
+ | * Looking at the ToF spectra gated on " | ||
+ | * The window file **S800_TOF_EFFICIENCY.win** includes all the spectra needed | ||
==== Checking Particle ID and rate at S800 FP ==== | ==== Checking Particle ID and rate at S800 FP ==== | ||
- | * Select SpecTcl window **S800_PID.win** in directory **/ | + | * Select SpecTcl window **S800_PID.win** |
* The three columns correspond to the PID determined with the **RF-FP** ToF (left), **OBJ-FP** (center), and **XFP-FP** (right) | * The three columns correspond to the PID determined with the **RF-FP** ToF (left), **OBJ-FP** (center), and **XFP-FP** (right) | ||
- | * The first (top) row corresponds to the Phillips TDC | + | * The first (top) row corresponds to PID spectra using the Phillips TDC |
- | * The second row corresponds to the MTDC with just the first hit included | + | * The second row corresponds to PID spectra using the MTDC with __just |
- | * The third row corresponds to the ORTEC TACs. Note that there is not **RF-FP TAC** | + | * The third row corresponds to PID spectra using the MTDC including the correct hit corresponding to the good ToF peak (see previous section) |
+ | * The fourth row corresponds to PID spectra using the MTDC gated on the " | ||
+ | * The fifth row corresponds to PID spectra using the ORTEC TACs. Note that there is not **RF-FP TAC** | ||
* You might need to adjust the limits of the spectra to get a good resolution | * You might need to adjust the limits of the spectra to get a good resolution | ||
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* Establish PID and measure rate | * Establish PID and measure rate | ||
- | * Determine | + | * Choose your favorite PID spectrum and determine |
* Take gates around the fragment of interest | * Take gates around the fragment of interest | ||
* Measure the beam intensity the appropriate faraday cup | * Measure the beam intensity the appropriate faraday cup | ||
* 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 | ||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | ==== Analysis line classic PPAC setup (Focus optics only) ==== | ||
+ | **THIS SECTION IS STILL IN PROGRESS** | ||
+ | |||
+ | * " | ||
+ | * 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 | ||
+ | |||
+ | * 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. | ||
+ | |||
+ | |||
+ | ==== Setting Optimization ==== | ||
+ | |||
+ | * 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/ | ||
+ | |||
+ | * 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**), | ||
+ | |||
+ | * Document optimized transmission with another run to disk to measure rate of fragment of interest at S800 FP | ||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | ====== Dispersion Matching Mode ====== | ||
+ | |||
+ | 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, | ||
+ | |||
+ | Charge-exchange experiments require typically this optics. In some cases, the beam used is < | ||
+ | |||
+ | * 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 | ||
+ | * Begin a new run on [[#Readout GUI|Readout GUI]] to assert new trigger condition | ||
+ | |||
+ | * Select **[[s800 SpecTcl|Spectcl]]** window **S800_DISPMATCH.win** | ||
+ | | ||
+ | |||
+ | * 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 | ||
+ | | ||
+ | * 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 < | ||
+ | | ||
+ | * 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 " | ||
+ | | ||
+ | * 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**, | ||
+ | | ||
+ | * 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. | ||
+ | | ||
+ | * 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. | ||
+ | {{: | ||
+ | |||
+ | |||
+ | ====== 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 | ||
+ | |||
+ | |||
+ | * Reaction setting to FP | ||
+ | * Start with Attenuator setting of unreacted beam and step up in intensity | ||
+ | * If necessary, set up beam blocker looking at **CRDC1.RAWS** and/or **CRDC2.RAWS** SpecTcl spectra (see **S800_CRDCS.win** SpecTcl window shown above) | ||
+ | * Click on label **I255 Slits** in the S3 page of Barney | ||
+ | * 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 | ||
+ | |||
+ | * If necessary, do the ToF corrections to improve the PID resolution (instructions [[During experiments# | ||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | ===== 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 [[S800 DAQ tools# | ||
+ | * 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 | ||
+ | * Using the [[S800 DAQ tools# | ||
+ | * Assign each wire to an inspect channel from the patch panel so that you can check their timings in the oscilloscope | ||
+ | * 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 | ||
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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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+ | * 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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