FT HODO Calibration tutorial
This tutorial explains the procedure needed to determine charge-to-energy and timing-offset constants for the FT Hodoscope.
To download, compile and run the program, refer to the following instructions:
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get a recent version of coatjava from the distribution site at http://clasweb.jlab.org/clas12offline/distribution/coatjava/ and point the COATJAVA environment variable to it:
wget http://clasweb.jlab.org/clas12offline/distribution/coatjava/coatjava-VERSION.tar.gztar xvfz coatjava-VERSION.tar.gzsetenv COATJAVA $PWD/coatjava -
get the calibration code from the git repository:
git clone https://github.com/JeffersonLab/clas12calibration-ft -
compile the calibration code:
cd clas12calibration-ft./build.sh -
jar files for each of the FT calibration projects will be built and saved in the lib folder
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launch the FTHodo calibration suite as follow:
./bin/ftHodoCalibHipo
The main panel will show up:
The calibration suite requires a HIPO file with the following banks:
RUN::config FTHODO::hits FTHODO::adc
To load a hipo file, click on H4 (stands for HIPO4 format) on the lower right side, and select the file to load.
For Charge-to-Energy calibrations the tab EnergyCalibration needs to be selected. Clicking on any Hodocope tile on the left-hand side of the suite will bring up the calibration histograms:
The top row corresponds to Layer 1 (thin) tiles and the bottom to Layer 2 (thick). The first two column show the Charge and Energy distributions of the selected tile, respectively. Clicking on a different tile using the Hodoscope view on the left-hand side will bring up the corresponding distributions.
The first column shows the charge distribution from ADC and the second the reconstructed energy determined during cooking. The red vertical line indicates the nominal position of the peak (1.2 MeV for thin and 2.65 for thick). The third column indicates all calibration constants for the selected sector (there are 8 sectors in the FTHodo, with odd sectors having 9 components and even having 20 components).
###Filling histograms
To accumulate statistics, click on the play button located under the Hodoscope view.
The analysis on the charge distributions is automatically performed by the GUI at a given event interval.
Once you are satisfied with the accumulated statistics, you can press the pause button (next to play) to stop the event accumulation. This should be typically done right after one the analysis fits are performed.
It is a good idea to load constants from CCDB for this run as a comparison to the new constants, and establish if the new constants need to be uploaded in CCDB. To do this, click on the Constants menu option and select CCDB.... The third histogram column should now show constants (for a specific sector) determined using the charge distribution from the loaded HIPO file (red points), as well as constants loaded from CCDB for this specific run (blue points). This allows to check if the constants in CCDB are reliable and whether uploading the new constants in necessary.
A careful inspection of all fits should be done before saving new constants in CCDB. A panel with all fits can be produced by clicking on the Histograms menu option, and selecting View all fits. The following view should pop up:
Fits that failed are indicated with the blue dotted fit line. These fits and any other fit that does not appear as a good description of the distribution should be adjusted. Ensure that all histograms plotted over 15 pages are inspected.
To adjust a specific fit, select the appropriate component from the hodoscope view (one needs to be attentive in selecting the appropriate Layer as well). Then click on the Histograms menu option, and select Adjust fit.... A panel, with initial fit parameters for the selected component opens up:
Adjusting the mean and Gamma of the Landau distribution is usually enough to produce a good fit. The fit is redone using the new initial parameter by selecting the Fit button. If the fit is adequate, selecting the Save button, saves the constant for the specific tile, and the histograms are updated. If no clear Landau peak is seen or there are not enough statistics for a reliable fit, one can select Save to Default where a default constant is saved. The Set button produces a function using the parameters selected (i.e. no minimisation is performed).
The timing-offset determination follows a similar procedure as the Charge-to-energy constant determination. Selecting the Tab TimeCalibration brings up a set of histograms related to the timing calibration. The first column shows the time-offset histogram for a wide range, where us the second Histograms, shows the same distribution, zoomed in. Fits are performed on this zoomed in distributions. The rightmost column shows the determined time-offsets for a specific sector. If CCDB constants are loaded (using the Constants menu and Load...), a comparison between the new constants (red) and constants from CCDB (blue) is done.
The procedure for inspecting and adjusting fits is identical as the one outlines for the Charge histograms. All fits should be inspected and adjusted where appropriate before constants are uploaded in CCDB.
Once all fits are inspected, the Charge distribution histograms and time-offset histograms, as well as determined constants should be saved as a PDF to be uploaded in the Hall-B logbook. This is done by clicking on the Histograms menu and selecting Print histograms to file....
Constants are saved by clicking on the Constants menu and selecting Save. The constants files should also be uploaded in the logbook.
All Fits and CCDB constants need to be documented in the Hall-B logbook. To do this, select Add content and fill out all appropriate fields. The appropriate logbook for documenting these is CLAS12CALIB, and use FTHodo as a Tag. Please notify, Raffaella DeVita, Nick Zachariou, and Dan Carman for any new calibrations being done.