Development of Photomultipliers

Photomultiplers(PMTs) available in liquid Xe are being developed in collaboraion with Hamamatsu Photonics Inc. There are two working version now. One is R6041Q, which has been used during studies with the small prototype and proved to operate stably in liquid Xe for long term. The other one is R5900-06 using the same photocathode material with R6041Q. The package of R5900-06 is the same one as R5900 listed in the catalogue of Hamamatsu. Specifications of these PMTs are summarised in the following table.
R6041Q R5900-06
PMT size57mmφ 27.7mm x 27.7mm
Photo-Cathode materialRb-Cs-SbRb-Cs-Sb
Size of effective area46mmφ18mm x 18mm
Q.E. at normal temperature10%-15%10%-15%
Dynode typeMetal channelMetal channel
Number of stages1210
Typical H.V.1000V800V
Current amplification1 x 1062.0 x 106

These two types employ metal channel dynode structure in order to reduce the lengths of PMTS. With micromachining technology closed proximity assembly of these thin electrodes has been achived. The schematical view of the struture is shown in Fig.1.

Fig.1 : Schematical view of metal channel dynode

R6041Q: Drawing and Voltage Divider Circuit

r5900-06: Drawing and Voltage Divider Circuit
Amount of material used in R6041Q and the holder is listed in the following table.
PMT Material Weight[g] Radius
Window Quartz 15.1 27.5mm
Stem Glass 32.8 22.6mm
Dynode SUS 12 x 2.02 25.5mm
Base G10 8.0 22.4mm
Tube SUS 6.4 ----

holder G10 29 mm
Spacer Acrylic11 mm
BackendAcrylic 5 mm

Modified version of R6041Q is under development. This version employs new metal chanel dynode stucture with more efficient collection efficiency. It is expected that transmission efficiency will increase without changing other parts of the PMT. Another version is also investigated. That is different from the compact PMT such as R6041Q and R5900-06, but uses a tradistional glass-tube resulting in higher quantum efficiency and transmission probability. The expected performance estimated with simulation by Hamamatsu are summarized in the following table.
R6041Q R6041Q-mod1 R7281Q
PMT length32 mm 32 mm 80 mm
Outer diameter57 mmφ57 mmφ 51 mmφ
Effective area41 mmφ41 mmφ46 mmφ
Q.E. at 200nm10% TYP10% TYP20% TYP
Transmission efficiency64% TYP79% TYP90% TYP
TTS0.75ns TYP0.75ns TYP 9.7ns TYP

In 2002 the situation developed. Hamamatsu adopted K-Cs-Sb photocathode instead of Rb-Cs-Sb. In addition it has an aluminum strip pattern to acquire 1.5 times higher QE than the previous ones. Quantum efficiencies as a function of wave length are shown in the follwing figure.

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S. Mihara Feb 18th, 2004