HV Scan Fall 2016

HV Scan Fall 2016

Data Taking

In order to determine the HV settings for the TOF PMTs a scan of the HV for all PMTs needs to be performed with the following conditions:

TOF Configurations:

• verify that the DAC values are set such that the base line for all PMTs is at about 100 ADC counts
• all thresholds for the discriminators should be set at -10. This value will correspond to about 10mV above base line in the TDC.
• the ADC readout window should be set to 100 samples
• NSA 25 samples
• NSB 3 samples
• CAEN TDC readout window should be large like 3000ns to include random hits to test integral non linearity correction

Beam Conditions (basic production conditions):

• 50nA current
• 50 micron diamond or equivalent thick radiator
• stable conditions
• NO prescale on Production-trigger
• LH target full

The following HV settings should be use for the scan (each run with >30M events! e.g. >30 files/run)

1. All HV at 1200 V (nominal)
2. All HV at -25V of nominal
3. All HV at +25V of nominal
4. All HV at -50V of nominal
5. All HV at +50V of nominal
6. All HV at -75V of nominal
7. All HV at +75V of nominal
8. All HV at -100V of nominal
9. All HV at +100V of nominal

Data Analysis

The analysis code is in the plugin TOFmon. It is in svn and can be retrieved with svn co https://halldsvn.jlab.org/repos/trunk/home/zihlmann/TOFmon See also the README file for additional information.

1. Analyze one file to generate the timing histograms for ADC and TDC and make sure that the timing cuts in the plugin select the hits with good timing for ADC and TDC data. If necessary adjust the timing cuts according to the histograms ADCtime and TDCtime. The positions of the timing peaks are coded with the variables:
   1. TDCtOffset
   2. ADCtOffset
2. In the same file verify that the TWalk histograms do have only one ridge. If there are more, this means the offset parameter TOF_TDC_SHIFT in the ccdb database for the 6-fold timing ambiguity of the CAEN TDCs is wrong and needs adjustment.
3. Analyze one file again with all adjusted parameters.
4. Determine the walk correction parameters by using the root script dof1.C. This script will generate a file walk_fitresults_run%06d.dat where %06d is the run number. Make sure this file is generated properly and located in the directory from where you run the analysis.
5. Analyze all files for a given run with the plugin TOFmon
6. Run the script findamp.C to find the MPV from the ADC response at various locations along the paddle for all paddles
7. Run the script viewampall.C to find the attenuation functions for each PMT.
8. After all runs are analyzed run the script gains.C to find the desired HV setting for chosen signal amplitude at the chosen distance from the PMT. The run numbers used in the analysis need to be adjusted for in the script.