Sciencetech PMH-04 is a thermal electrically cooled version of the model PMH-02 analog housing. By cooling the photomultiplier tube to -20°C, it substantially helps the detection of weak signals by reducing the amount of dark current. Like the PMH-02 analog housing, the model PMH-04 includes all PMT support electronics such as network divider, low noise preamplifier and high voltage power supply. The control panel is also the same as PMH-02 such as the high voltage is adjustable through a control lead (gain of 100W per input volt), the LCD readout shows actual cathode voltage or output signal, and there are separate controls for response time, offset, and gain. The output signal is analog, but can be digitized through Sciencetech's optional external single channel AD data acquisition system (via a BNC cable) for interface to a computer. Note: Cooling temperature is dependent on ambient temperature and temperature of the water used to cool.

Thermo-Electric Cooling Operation
The Photomultiplier Tube is inserted into a double chamber environment where the inner most chamber is cooled by a Peltier cooler capable of maintaining a temperature of -20ºC. The inner chamber is also enclosed in an outer nitrogen gas chamber for added insulation. To dissipate the heat from the Peltier cooler, a water cooling loop is used and hence the requirement of an external water recirculator. The output window is heated to prevent water condensation from building up. The housing includes connectors for nitrogen purging of the outer nitrogen insulation chamber, and connectors for the Peltier cooler water cooling loop. Warm-up time is 10 minutes. Note: Cooling temperature is dependent on ambient temperature and temperature of the water used to cool.

Standard Fixed Temperature
In the standard configuration, the Peltier cooler operates at its lowest temperature setting of -20ºC for maximum dark current reduction and is non-adjustable.

Optional Variable Temperature Controller
An optional external Variable Temperature Controller unit with thermistor allows the Peltier Cooler temperature to be adjustable. The temperature can be set by the external temperature control unit or through a computer via an RS-232 interface. A full featured Windows based software application and Labview module is included for computer control. However, this temperature control software is independent of the Sciencetech Sci-Spec data acquisition software that captures the data from the Cooled PMT Housing.

Optional Water Recirculator
The current PMH-04 Housing requires an external water recirculator to keep the Peltier Cooler cooled. Sciencetech sells the Model 160-REC water recirculator as an option for this purpose, although any third party recirculator would work. Sciencetech will soon replace this water cooling loop with a heat sink and forced air cooling fan such that an external water recirculator is not required. Please inquire about this availability at the time of ordering.

Cooled PMT Tubes Available
S1 type photocathode tubes requires cooling for optimum operation. Please see selection of PMT tubes available.

Replacement of PMT
Since most PMT share the same socket style, the PMT housing can accept more than one type of PMT. It is therefore possible for the customer to purchase one PMT housing, and multiple PMT of the same socket style and interchange them when required. Please read the manual to assure safe exchange of the PMT inside the housing to avoid electrical shocks and damage to tubes etc.