Preliminary Results of the Test Run at SLAC

Petra Hüntemeyer

This analysis based on ...• two weeks of data taking • or 707 runs each with between

2500 to 5000 recorded ‘events’• or 2 million recorded ‘events’• gas fillings: air, nitrogen, air-

nitrogen mixtures, ethylene• pressures between 3 and 760 torr• readout from one of two PMTs

Analysis variables are...

• gas type/mixture• pressure• gas flow bit• beam charge• signal in the signal tubes• signal in the blind tubes• HV applied to the PMT

Cut Flow Cut Remaining events

Range cuts rejectingcorrupted data 2182604Select one of theapplied HVs 1585729Beam quality 1174039First pass:AirNitrogenNitrogen (flowing)

364341 294092 63974

First Pass Data

• Signal PMT

First Pass Data

• Signal PMT

First Pass Data

• Signal PMT

First Pass Data

• Signal PMT

Background subtraction

Background Subtraction

Corrected Signal Scorr = Sraw - Pave - f eth S blind

S raw : raw signal Pave : average pedestal S blind : blind tube signal

f eth : factor from Sraw / Sblind ethylene runs

Linear Region

• Definition of a range where signal vs beam charge behavior is linear

Yield Calculation

Y = Scorrfconv / bc acc / sen

• Scorr : corrected signal [ADC counts]• fconv : conversion factor, ADC counts to pC • bc : beam charge [ e-]• acc : geometrical acceptance• sen : sensitivity from calibration folded with

Bunner spectrum

Calibration

Preliminary Result : Air

Uncertainties: Air (incomplete!)

Statistics < 1 %

Geometrical Acceptance 3 %

Sensitivity (calibration) +Spectrum (assumption)

7 %

ADC to current conversion 3 %

Pedestal and Background 1 %

Beam charge 5 %

Additional systematics 3 %

Total 10.1 %

Preliminary Result: N2

Preliminary Result

How does this compare with earlier

measurements? Kakimoto et.al,

Nucl. Inst. And Meth. A372 527 (1996)

Preliminary result from this test run

@ 28.5 GeV: 5-6 photons per m per e-

Analysis Conclusions

• promising preliminary results from a first look at the data

• a large amount of data collected during test run remains to be analyzed and more detailed systematic studies have to be performed

• insights from test run and analysis serve as input for the preparation of the anticipated experiment at SLAC

Conclusions

• purpose of T461: test run for a more sophisticated experiment proposed at SLAC

• we observed PMT signals in coincidence with the beam whose features are consistent with fluorescence

• the enhancement of the pure nitrogen signal over that in air is consistent with what we expect from earlier fluorescence measurements

• we observed a non-linear behavior of the fluorescence signal versus beam charge in the excess of 2 109 e-

• we also observed a linear behavior below 109 e-

• a study of the blind tubes indicates that the beam halo related backgrounds are relatively small