Specifications

PERFORMANCE

All photomultiplier tube specifications are furnished by the PMT manufacturer. The Model 265A Base includes an appropriate voltage divider network for the tube elements.

CONTROLS

Internal adjustments are included for the focus electrode and for the second and twelfth dynodes.

INPUTS

HIGH VOLTAGE –3 kV maximum at 2 mA maximum for bleeder network. SHV connector.

AUXILIARY Last four dynodes are available at pins in the Auxiliary connector for optional external voltage stabilization; MS3112E12-10-S or Bendix PT02E-12-10S connector.

OUTPUTS

ANODE Negative timing signal, 50 W, dc-coupled, back-terminated; very good pulse quality for signal currents to 0.5 A with the Burle 8575; BNC connector.

DYNODE Positive linear signal from the ninth dynode, capacitively-coupled, high impedance (Z_o ~1 MW ); BNC connector.

ELECTRICAL AND MECHANICAL

WEIGHT (Net)

265A PM Base   0.63 kg (1.4 lb).
218 Shield   0.45 kg (1 lb).

WEIGHT (Shipping) 265A PM Base   1.3 kg (3 lb).
218 Shield   0.9 kg (2 lb).

DIMENSIONS

265A PM Base   7.62 cm (3 in.) diam X 20.32 cm (8 in.) long.

218 Shield   7.62 cm (3 in.) diam; assembled Models 265A and 218, 33.0 cm (13 in.) long.

RELATED EQUIPMENT

The anode timing signal should be furnished to a fast discriminator such as the ORTEC Models 583B, 584, or 935, when using either NaI(Tl), liquid, or plastic scintillators. A Model C-25-12 50-W cable assembly is available as an accessory for this purpose.

For single-photon counting insert a fast amplifier, such as the Model VT120, between the anode output and the discriminator input.

The linear output from the ninth dynode is normally processed through an ORTEC Model 113 Scintillation Preamplifier and a shaping amplifier such as the ORTEC Models 460, 570, 572A, or 575A.

An ORTEC Model 218 Magnetic Shield is recommended to reduce the interference from either the earth's magnetic field or from stray-magnetic fields from other equipment.

High voltage, at the level recommended by the manufacturer of the PMT, can be furnished from a high-voltage power supply such as the ORTEC Model 556. The mating cable, C-36-12, is also available for connecting the Model 265A to the Model 556; C-36-12 consists of 3.66 m (12 ft) of RG-59A/U 75-W cable with two SHV connectors assembled and ready to use.

218 Magnetic Shield

An accessory magnetic shield (Model 218) is available for the Model 265A Photomultiplier Tube Base. The magnetic shield isolates the photomultiplier tube from ambient magnetic fields that would introduce error into the output signal; it also isolates the sides of the PMT from ambient light. The magnetic shield complies with standard photomultiplier tube dimensions.

Fig. 1  Typical anode OUtput with a Burle 8575 Photomultiplier Tube.

Fig. 2  Pin Assignments

ORDERING INFORMATION