1. Pedestal Stability and Sparsification Nick Woods UNCW July 29, 2005

2. Pedestals Each ADC channel has its own “zero”–called a pedestal. The pedestal can be fit with a Gaussian distribution with a mean value and sigma. Pedestal Distribution for Channel 1421 During Calibration Run 4076

3. Sparsification In order to prevent readout from occuring below a certain line, each counter is given an ADC threshold below which no readout will be done. This process is known as Sparsification. For Primex: Sparsification = Ped Mean + 5 ADC Counts Pedestal Distribution for Channel 1421 During Calibration Run 4076

4. Sparsification Pedestal Distribution for Channel 1421 During Calibration Run 4076 Sparsification In order to prevent readout from occuring below a certain line, each counter is given an ADC threshold below which no readout will be done. This process is known as Sparsification. For Primex: Sparsification = Ped Mean + 5 ADC Counts

5. Pedestal Stability Throughout the course of the experiment, the pedestals can fluctuate. However, the sparsification is a set value. The task of this investigation is to discover the stability of each pedestal, and how that stability relates to the quality of the data. ???

6. Pedestal Shifting If the pedestal for a particular channel makes a NEGATIVE shift during the experiment, data can be LOST!!! Pedestal Shift-Channel 1423, Run 5155 Blue = Spars. Ped. Red = Ped. 5155

7. Discovering “Bad” Channels 1. Create histogram for each run 2. Extract channels where (Pedestal – Sparsification) < -6 3. Put these values (run number, channel number, difference) into the database This information can be accessed by logging into the book_keeping database in mysql, and viewing the bad_spars table. +------+------+--------------+ | run | id | pedSparsDiff | +------+------+--------------+ | 5060 | 114 | -6.025 | | 5060 | 1391 | -6.575 | | 5060 | 1421 | -6.625 | | 5060 | 1422 | -6.475 | | 5060 | 1423 | -6.825 | +------+------+--------------+ Example: mysql> select * from bad_spars where run = 5060;

8. Summary 1. Pedestal Stability investigation complete. 2. Database created and filled with runs, channels, and differences (34,950 entries). 3. Very few channels appear consistently, most runs have only 5-10 bad channels.

9. Thank You Mark Ito Ashot Gasparian Mike Wood Vasily Mochalov Dustin McNutly Liping Gan