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SHIELDING

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Magnetic Shielding   •   Electrostatic Shielding   •   RFI Shielding


 

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Electrostatic Shielding
RFI Shielding
MAGNETIC
SHIELDING
All Products for Research cooled photomultiplier housings contain high permeability magnetic shields as an integral element of the housing. There shields are specially manufactured for Products for Research of 1 mm. thick, heli-arc welded and annealed cylinders. The maximum permeability of Products for Research standard magnetic shields for D.C. magnetic fields is 4.5 x 10^5 gauss/oersted and the induction at that point is 3000 gauss.

The saturation induction of this alloy is 7500 gauss. Finally, the shield is designed to extend the recommended distance of 1/2 the cathode diameter in front of the photocathode. This Products for Research standard system provides full magnetic shielding for practically all situations of photomultiplier application. In addition, for those applications in extreme fields, customized magnetic shielding is also available.


 

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Magnetic Shielding
RFI Shielding
ELECTROSTATIC
SHIELDING
The electrostatic shielding in Products for Research cooled housings is carefully designed to protect the photocathode and dynode system from the adverse effects of extraneous electrostatic fields. Internal automatic connection is made between the tube socket assembly and the housing.

This design makes it possible to put the shield at high negative voltage or at ground, simply by using the appropriate interchangeable tube socket assembly. This technique also allows the shield to be put at the potential on one of the dynodes as some research seems to indicate is desirable.


 

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Magnetic Shielding
Electrostatic Shielding
RFI
SHIELDING
All Products for Research housings are available shielded against Radio Frequency Interference. Unitized exterior cases are made possible by insuring metal to metal contact, through the use of precious metal gasketing between conductive surfaces. In addition, all power feed connectors to the housing and socket incorporate decoupling networks to insure that all RFI is filtered out. All Products for Research RFI shielded housings are rigorously tested using broad band high gain photon counting equipment.

The tube for which the socket assembly is built is installed in the housing and one meter of coaxial cable is attached to the high voltage connector (this provides an antenna system). The signal connector is connected to the photon counting equipment with the lower discriminator set a 50 mV. This system is located one meter from a high frequency electric arc source. Under these conditions, the photon counter must indicate no counts on the 10 count per second full scale setting. In addition to this, the unique satisfaction guaranteed policy of Products for Research insures that even the most unusual shielding problems will be resolved.


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