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 size||57mmφ ||27.7mm x 27.7mm
|Size of effective area||46mmφ||18mm x 18mm
|Q.E. at normal temperature||10%-15%||10%-15%
|Dynode type||Metal channel||Metal channel
|Number of stages||12||10
|Current amplification||1 x 106||2.0 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
|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 ||Acrylic||11 mm|
|Backend||Acrylic|| 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.
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
| ||R6041Q ||R6041Q-mod1
|PMT length||32 mm ||32 mm ||80 mm
|Outer diameter||57 mmφ||57 mmφ|| 51 mmφ
|Effective area||41 mmφ||41 mmφ||46 mmφ
|Q.E. at 200nm||10% TYP||10% TYP||20% TYP
|Transmission efficiency||64% TYP||79% TYP||90% TYP
|TTS||0.75ns TYP||0.75ns TYP|| 9.7ns TYP
Feb 18th, 2004