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Product Name: 265A Photomultiplier Base
Product Description
For use with 12-stage PMTs that fit standard 21-pin sockets
Designed for fast-timing applications
Excellent pulse fidelity for a wide range of signal currents
High-impedance linear signal from dynode, and dc-coupled anode signal at 50-W impedance for timing
Excellent for single-photon counting
Magnetic shield available
The ORTEC Model 265A Photomultiplier Base is a mechanical assembly and a resistive voltage divider network, with appropriate capacitive decoupling, for operation of 12-stage photomultiplier tubes (PMTs). It is particularly suited to applications requiring fast timing or single photon counting. The Model 265A accommodates the following types of PMTs.
12-stage PMTs that fit standard 21-pin sockets, including:
Hamamatsu R329, R1332, R1333
Burle 8575, 8850, C31000M.
These PMTs offer excellent charac-teristics for both timing and energy resolution. The Model 265A PMT Base structure complements the tube characteristics by maintaining good pulse fidelity through a wide range of signal currents (Fig. 1).
Negative high voltage is applied to the cathode, and the anode is operated essentially at ground potential. This facilitates the incorporation of several features that augment the fast-timing performance. The anode output is dc-coupled, with the anode connected to ground through a 50-W load resistor. This eliminates the base-line shift caused by varying counting rates in ac-coupled systems. It also suppresses reflections by providing back-termination for the anode output connection. Each of the last four dynodes is also available externally through the contacts of the auxiliary connector. These connections allow external voltage stabilization for the last four dynodes of the PMT by using external voltage supplies. Internal trimmer controls permit optimum adjustment of the voltage distributed to the focus electrode, and to the second and twelfth dynodes.
Two outputs are furnished from the Model 265A. The negative signal from the anode is optimized for timing applications, while the positive, linear signal from the ninth dynode is intended for energy measurements. For fast scintillator applications, the anode signal is connected directly to the input of a constant-fraction timing discriminator via a 50-W coaxial cable. For single-photon counting a fast amplifier is typically inserted between the anode output and the discriminator. In scintillator applications the ninth dynode output is normally connected to the input of a preamplifier, such as the ORTEC Models 113 or 142IH. The output pulses from the preamplifier are amplified and shaped for energy spectroscopy through an amplifier such as the ORTEC Models 460 or 575A.
Excellent results for both timing and energy measurements can be obtained with fast plastic scintillators, fast liquid scintillators, and NaI(Tl). The Model 265A PMT Base is also ideal for single-photon applications (see Application Note AN51).
Company Details
From its inception as a small enterprise founded by scientists and engineers from the Oak Ridge National Laboratory, our business and reputation for excellence in scientific instrumentation have grown substantially. Along with that growth came... more
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