• Sockets and Overcaps
Only sockets approved by ET Enterprises must be used.
Components fixed to the socket must not distort the natural pitch circle diameter of the contacts.
From January 1990 PES (polyethersulphone) replaced DAP and PTFE previously used for sockets and overcaps and the following precautions apply:
- When soldering to the contacts the temperature must not exceed 220°C.
- Sockets or overcaps must not be allowed to come into contact with the following substances: Cyanoacrylate adhesives, Acetone, Chloroform, Dichloromethane (paint stripper).
Adhesives which are suitable for this material are Epoxy Resins, Polyurethane and Silicones.
Prior to bonding the surface should be cleaned with a suitable alcohol.
Electrical connections must not be made to socket contacts marked ic.
• Photomultiplier Pins
The pins on the base of the photomultiplier should not be modified in any way whatsoever without prior reference to ET Enterprises. Never solder directly to the pins of a hard-pin photomultiplier.
When inserting or removing the photomultiplier from the socket, maintain the tube perpendicular to the plane of the socket and avoid undue force.
• Photomultiplier Envelope
Remove the window protector disk before use.
Unless otherwise stated, this will safely withstand an over pressure of one atmosphere.
If additional support or attachments to the envelope are necessary please contact ET Enterprises for advice.
If installed in a vacuum or reduced pressure environment, photomultipliers with a blue overcap must have a 1mm diameter hole drilled in the overcap to allow trapped air to escape.
• General Operation
Do not exceed the maximum ratings in the specifications or the overload voltage on the test ticket.
Photomultipliers are adversely affected by magnetic fields and suitable mu-metal shields should be used wherever possible.
Photomultipliers are generally robust, but will not tolerate extremes of heat, mechanical shock and, unless adequately screened, external high voltages. For use under adverse conditions, please contact ET Enterprises for advice.
For high stability, care must be exercised in mounting tubes to prevent external charging and discharging caused by high voltages applied to the photomultiplier or from external apparatus.
Photomultipliers should be kept in the dark prior to use otherwise dark current will be temporarily increased.
The housing into which the tube is fitted must be light tight.
To obtain the lowest dark current the tube should be clean and dry, especially the base, cleaning with methyl alcohol is recommended. Care must be taken to avoid damaging the cathode pin connection strip on uncapped tubes.
If the tube is operated with negative high voltage, increased dark noise may result. In this situation, only PTFE or a similar high quality insulator should be in direct contact with the glass envelope.
Unless the operating conditions have already been determined, it is recommended that the high voltage supply be increased gradually until the required setting is obtained.
Shielding material must be maintained at cathode potential. Failure to do this will impair performance and reduce photomultiplier life. For -HV applications, the window must be kept at least 4mm from any earth plane and any locating rings used near the window must be made from PTFE (Teflon). +HV is recommended for pulsed applications such as scintillation and photon counting.
• Storage
It is recommended that photomultipliers are stored in the dark. Incident light on photomultiplier tubes should be avoided or subdued.
Exposure to bright light, especially fluorescent or sunlight will excite phosphorescence in the glass and photosensitive layers of the photomultiplier. Do not store or use photomultipliers in a helium rich atmosphere. This will diffuse through the envelope and destroy the internal vacuum.
Photomultipliers should not be exposed to moisture, high humidity, vibration, shock, extremes of temperature and dirt.
NOTE: Failure to observe these precautions and recommendations may invalidate the guarantee.