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Photomultiplier detection system

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  • Compact Size and easy to Use
  • Inexpensive, complete Package
  • Operates in Analog or Photon Counting Modes
  • Detection from 185 to 900 nm
  • LCD display of output signal

 

For spectroscopy and microscopy experiments in the UV/Vis/NIR region of the spectrum, a photomultiplier tube (PMT) is the ideal detector for quantitative low light level measurements. A PMT is extremely sensitive, with very wide dynamic range so it can also measure high levels of light. PMT’s are also very fast so rapid changes in optical signals can be reliably monitored. As a practical matter, PMTs are durable, long-lived, and economical.

Optical Building Blocks provides a simple, self contained PMT housing that operates in either analog or photon counting modes with the flick of a switch. This ambient PMT housing is ideal for standard side-on PMTs that are used from 185 to 900 nanometers. It has a very low dark count for a non-cooled PMT housing providing a dark count of only ~ 50 to 500 counts per second (cps) depending on the PMT selected.

PMT's are better than photodiodes and APD's for low light detection

Although the quantum efficiency (QE) of a PMT is less than that of a silicon photodiode or avalanche photodiode (APD), a PMT has a much lower limit of low light detection due to the high current amplification (~ 107) of the electron multiplier in the PMT. It is because of this large gain and low noise that a PMT provides significantly better low light sensitivity than a photodiode or APD.

Looking for NIR Detection?

For NIR detection beyond 900 nm please take a look at our CoolOne cooled PMT housing for photomultiplier detection from 185 to 1,200 nm and also our InGaAs detectors for detection from 0.8 to 1.9 μm.

The OBB ambient PMT housing includes the following

 

  • On/off switch
  • Complete analog and photon counting circuitry
  • Analog or photon counting mode/output switch
  • Line voltage power supply
  • High voltage power supply
  • LCD display of PMT high voltage or measured analog signal
  • Signal out BNC connection
  • High voltage adjustment knob
  • External high voltage control input BNC connection (for optional external control)
  • RF shielded case
  • Internal socket for most 1 1/8-inch side-on photomultiplier tubes

 

OBB’s photomultiplier detection system is very convenient and easy to use. It is built as a complete unit using modern design techniques and components. Everything needed to quantitate the intensity of light is packaged into a compact, attractive housing that attaches conveniently to your experiment. There are no unsightly boxes for power supplies or a multitude of cables tangled on your bench-top. The system incorporates a high voltage supply, all detector electronics, and the controls in a compact, attractive housing that also contains the PMT. You have a choice of standard PMTs to choose from or you can select from any other 1 1/8-inch side-on photomultiplier tubes that operate from -200 to -1,100 Volts DC. The PMT high voltage is shown on a digital display on the housing or you can select to show the actual analog signal from the PMT with just a flip of a switch. The high voltage can be adjusting manually or controlled externally with a signal at the “External Voltage Control” BNC. Power is delivered from an external AC adapter that is included.

 

OBB’s ambient PMT housing will accept a wide variety of side-on 1 1/8-inch diameter photomultiplier tubes that operate from -200 to -1,100 Volts DC. It is optimized for PMTs with uniform dynode chains. PMTs are normally selected based on their wavelength response and their noise and/or sensitivity characteristics. Below are details for two of the most commonly selected PMTs offered as standard selections for use with our PMT housing. We can and do offer other special PMTs for custom applications.

185 to 650 photon counting or analog PMT

Specifications

Spectral Response 185 to 650 nm
Photocathode Material Multialkali
Effective Area of PMT 8 x 24 mm
Supply Voltage 1250 V dc
Cathode Sensitivity
Quantum Efficiency at 300 nm (Peak) 
Luminous 
Radiant 400 nm (Peak)

19 % typ.
60 µA/lm typ. 
60 mA/W typ.
Anode Sensitivity (at 1000 V)
Luminous
Radiant at 400 nm

400 A/lm typ. 
4 x 105 A/W typ.
Gain 6.7 x 105 typ.
Anode Dark Current 
(After 30minute Storage in the darkness)
0.1 nA

 

185 to 900 photon counting or analog PMT

Specifications

Spectral Response 185 to 900 nm
Photocathode Material Multialkali
Effective Area of PMT 8 x 24 mm
Supply Voltage 1250 V dc
Cathode Sensitivity
Quantum Efficiency at 260 nm (Peak) 
Luminous 
Radiant 400 nm

25.4 % typ.
250 µA/lm typ. 
74 mA/W typ.
Anode Sensitivity
Luminous
Radiant at 400 nm

2500 A/lm typ. 
7.4 x 105 A/W typ.
Gain 1 x 105 typ.
Anode Dark Current 
(After 30minute Storage in the darkness)
3 nA

 

Control Specifications

Dual Mode, Analog/Photon Counting Photomultiplier Detection System Display LCD display of high voltage or signal
Controls On/Off switch
Analog/Digital Mode switch
Voltage/Signal Display switch
Voltage Adjust potentiometer
Analog Gain selection
Analog Time Constant selection
Analog Offset
BNC Connectors Signal Out
External Voltage Control

Specifications

Physical Specifications

Dimensions (WxDxH) 4  x 4 x 8 inches
Weight 4 lbs

 

High Voltage Power Supply Specifications

Input ± 15 VDC, 250 mA
High Voltage -200 to -1,100 VDC manually adjustable LCD displays actual cathode voltage
External High 0 to +5 VDC (0 = -200 V, 5 = -1,100 V)
Voltage Adjust Continuously adjustable
Input Regulation ± 0.05% max. (for 15 V ± 1 V input).
Load Regulation ± 0.05% max.
Ripple 100 mV p-p max.
Temperature Coefficient ± 0.01% max. (+5 to 40°C)
Drift ± 0.03%/hr. max. (after 15 minute warm-up)

 

AC Adapter Specifications

Input 115 or 220 VCA (specify at time of order)
Output ±15 VDC, 250 mA

 

Analog Mode Specifications

Gain Settings: 1 µA = 1 V
0.1 µA = 1 V
0.01 µA = 1 V
0.001 µA = 1 V
Time Constant Settings:
(with Corresponding Analog Frequency
0.05 msec (20 KHz) 
0.5 msec (2 KHz) 
5 msec (200 Hz) 
50 msec (20 Hz) 
500 msec (2 Hz)
Offset Correction: ± 50 nA
Signal Output on BNC connector: Analog voltage

 

Photon Counting Mode Specifications

Linear Dynamic Range: 5 orders of magnitude*
Dead Time: 250 ns
Signal Output on BNC connector: TTL

* Linear dynamic range of the OBB photon counting PMT housing. The intensities were produced by attenuating the fluorescence emission of a fluorescein sample with neutral density filters.