Tuesday, April 11, 2023Philip Symes

Using PMT Gain Averaging as an Improved Method for Measuring Drift Points

Philip Symes,University of Sussex

MINOS “Week In The Woods” Ely, MN

June 2005

LI Calibration Progress

April 11, 2023LI Improvements by Philip Symes

1 The ProposalPMT gain averaging

• From options presented at last meeting, we decided to concentrate on

PMT gain method.• Can use this method without any changes to online data taking• Main advantages are to decreases database load and remove

vulnerability to h/w changes, etc

* Uncertainty on gain measurement 5.1% from 1k pulses

Option:

Online

factor

Offline

factor

h/w

robust

new

code?

Dead

time

stat.

prec’n

Std. LI 1 1 No No, but...

0.1% 1%

gain, pmt

1 0.008

Yes Some 0.1% 0.45%

April 11, 2023LI Improvements by Philip Symes

2 PMT Response over Time

• Must be sure that all strip-ends move together… • So used CalDet LI data over 30 hour period to get necessary (2-3%) response change

April 11, 2023LI Improvements by Philip Symes

3 Linear Relationship between Stripend Drift & Stripend Gain

• The CalDet run drift changes agree with the gain changes, as we would expect.• The gradient of the line is 1.072(79).

April 11, 2023LI Improvements by Philip Symes

4 Linear Relationship between Stripend Drift & PMT Gain

• The agreement between PMT gain change and stripend drift is also good: 1.046(72).• Using PMT gain averaging is a viable alternative to standard stripend drift LI

April 11, 2023LI Improvements by Philip Symes

5 Drift with Gain Correction

• The PMT gain method is taking out the systematic changes leaving only statistical scatter

Uncorrected

Corrected

April 11, 2023LI Improvements by Philip Symes

6 Drift point dependence on nominal gain

• A plot of variation of the stripend’s drift compared to the PMT’s drift against nominal gain• This is a VERY SMALL 2nd order correction (~10-4)• Effect looks more marked at FarDet (better statistics)

AfterBefore

April 11, 2023LI Improvements by Philip Symes

7 Summary Of Proposal

• Keep online procedure the same for time being (can go back to standard LI if problems found later)

• Use average PMT gain changes from gain point anchors to calculate drift in offline

• Method solves PULSERDRIFT DB table size problem: reduces to 0.8% of current size

• New method could also reduce the amount of LI drift point data that needs to be taken (less deadtime)