Test Results from Quality Control Measurements of Phototubes for the CMS-CASTOR Calorimeter

Presented by*

S. Aydın1, I. Dumanoglu1, G. Onengut1, S. Ozturk1 and K. Sogut2

1 University of Cukurova, Department of Physics, Adana, TURKEY.2 University of Mersin, Department of Physics, Mersin, TURKEY.

11th Vienna Conference on Instrumentation, Vienna, Feb 19-24, 2007.

The testing systems for measuring the gain and timing parameters

Results of the measurements3. Timing Parameters

• We used a 337 nm pulsed laser source for measuring the timing parameters.• Laser ray passes an NDF and then hits a beam splitter. The reflected light is directed to a PIN diode and the transmitted light is sent to PMT after passing through few more NDFs. • PIN diode that was powered with 7 V was used to trigger the oscilloscope. • PMT signal was evaluated with a LeCroy oscilloscope that has an OS itself. • Rise time, pulse width and transit time values of each PMT are measured.

System to measure the timing parameters

The CMS-CASTOR Detector

• The very forward region of the CMS will be completed by the ZDC and CASTOR calorimeters.• They will locate after the HF detector and cover almost the whole angular region. • CASTOR will investigate the baryon rich very forward rapidity range (5.2 to 6.6) of central Pb+Pb collisions @ 5.5 TeV.• The physics goal of the calorimeter is to study the anomalistic events called centauros and stranglets. Such events have been detected in the earlier cosmic ray experiments.• CASTOR will locate at 14.36 m from the interaction point. It surrounds the beam pipe azimuthally and is divided into 16 sectors. Longitudinally it consists of 18 successive layers that are made of tungsten plates. Tungsten plates are followed by the quartz plates.

Hamamatsu R5380 PhototubesIn the CASTOR calorimeter hadronic and photonic contents of the interactions will be determined by the detection of the Cherenkov light. Cherenkov light produced in the quartz plates will be read by PMTs. It is transmitted to the phototubes through the aircore light guides.

Phototube Specifications

Calorimeter will be equipped with 224 Hamamatsu R5380 phototubes (PMT).

Schematic view of PMT.

Gain Testing System

• Gain measurements are done in the light-tight boxes. • A 12 V, 20 W halogen lamp is used as the light source.• Light comes to PMT through a Neutral Density Filter (NDF, factor=2). • Currents for gain measurement are read by a picoammeter.• Light intensity inside the box is monitored by a spectrometer to make sure the stability of the measurements each time. • All the gain measurements are performed with a high voltage supply that was to range from 500 V to 1600 V with a 50 V step at each measurement. • Data acquisition is done with a LabView code.

HVPower Supply

Laser I nside the box

HVPower Supply

Laser I nside the box

Schematic view of timing setup

Screenshot of oscilloscope

PMT Gain = Anode Current / Cathode CurrentMeasured Value : 5831 @ 1100 V

Num

ber

of P

MT

s

Gain

Anode Dark Currents vs HV

-5.00E-09

0.00E+00

5.00E-09

1.00E-08

1.50E-08

2.00E-08

2.50E-08

300 800 1300 1800

High Voltage (V)

An

od

e D

ark

Cu

rren

t (A

)

2. Anode Dark Currents

1. Gain Measurements

Parameters Value

Anode Dark Current < 10 nA

Anode Pulse Rise Time < 5 ns

Electron Transit Time < 25 ns

Pulse Width < 15 ns FWHM

Average Anode Current < 100 µA

Preferred Values of Parameters

Nu

mb

er

of P

MT

s

Pulse Width (ns)

Nu

mb

er

of P

MT

sN

um

be

r o

f PM

Ts

Transit Time (ns)

Rise Time (ns)

Conclusion• We measured dark currents, gains and timing parameters of 34 PMTs.• All the measured timing parameters were below the requirements of the CASTOR Group. • The average PMT gain is around 6000 which is acceptable during the operation of CASTOR.• All the dark current measurements were also in the acceptable range.