Even changing the orientation of a photomultiplier in the Earth's field can show a detectable effect. We offer a selection of different types of magnetic shields to cover the entire range of ET Enterprises' photomultipliers.

There is more than one type of shield available for some tube types and the final choice of shield will depend on the magnitude of shielding required. Magnetic fields affect the collection efficiency and the gain of a photomultiplier, to a degree dependent on the type of dynode structure. Performance curves for the four multiplier structures are given in the technical document: understanding photomultipliers. Information is also given in the individual data sheets.
integral magnetic shields

These are offered for all end-window photomultipliers up to 52 mm diameter. The photograph to the right shows a photomultiplier fitted with an integral magnetic shield. A 0.125 mm thick mumetal* sheet is wrapped around the envelope and protected by an insulating sleeve. There is direct electrical contact from the shield to the cathode pin. These are the most cost effective, but other options with a higher degree of shielding may be necessary in place of, or in addition to, an integral shield.

Split cylinder magnetic shields

These are available for end window photomultipliers up to 52 mm in diameter. The shield is in the form of a split cylinder of thickness 0.5 mm. An internal grip pad that adheres to the photomultiplier is included. The range is listed in the table below.

Length A
Length B
Ø pmt
MS19A 75 22 19
MS25A 39 29 25
MS30A 76 33 30
MS30B 102 33 30
MS38A 83 41 38
MS52A 76 56 52
MS52B 102 56 52
MS52C 133 56 52
MS52D 152 56 52

Contoured magnetic shields

These 0.5 mm thick magnetic shields are available for side-window, and end window photomultipliers with diameters in the range 52 mm to 200 mm.

The range is listed in the table below. To view an outline drawing click on the shield type number.

Diameter mm
MSSW 30 (side window) B11A no lugs
MS52E 52 B14A,  B21
MS52F 52 B15B,  B19A
MS75/90 75 B15B,  B19A
MS75/90 90 B15B,  B19A
MS130A 130 B15B,  B19A
MS130B 130 B14A
MS200A 200 B20

A comprehensive selection guide for individual photomultiplier types can be viewed on this page. An insight into magnetic field theory is provided on this page.

It is important to connect the magnetic shield to the photocathode potential; this will prevent noise generation from potential gradients across the glass envelope of the photomultiplier.

Contact us for further information.
Request a quotation.

* Mumetal is a registered trade mark of Magnetic Shield Corportion.

© ET Enterprises Limited 2011-2015
ET Enterprises is a trading name of ET Enterprises Limited. Registered in England & Wales, company number 06081468.