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PHOTOMULTIPLIER TUBES

PHOTON IS

OUR BUSINESS

Basics and Applications

THIRD EDITION

▲ Photomultiplier Tubes

▲ Photomultiplier Tube Modules

CONTENTS

• CHAPTER 1 INTRODUCTION
  • 1.1 Overview of This Manual
  • 1.2 Photometric Units
    • 1.2.1 Spectral regions and units
    • 1.2.2 Units of light intensity
  • 1.3 History
    • 1.3.1 History of photocathodes
    • 1.3.2 History of photomultiplier tubes
  • References in Chapter - PHOTOMULTIPLIER TUBES CHAPTER 2 BASIC PRINCIPLES OF
  • 2.1 Photoelectron Emission
  • 2.2 Electron Trajectory
  • 2.3 Electron Multiplier (Dynode Section)
  • 2.4 Anode
  • References in Chapter - OF PHOTOMULTIPLIER TUBES CHAPTER 3 BASIC OPERATING METHODS
  • 3.1 Using Photomultiplier Tubes
    • 3.1.1 How to make the proper selection
    • 3.1.2 Peripheral devices - High-voltage power supply - Voltage-divider circuit - Housing - Integral power supply module
    • 3.1.3 Operating methods (connection circuits)
    • PHOTOMULTIPLIER TUBES CHAPTER 4 CHARACTERISTICS OF
• 4.1 Basic Characteristics of Photocathodes
  • 4.1.1 Photocathode materials - (1) Cs-I - (2) Cs-Te - (3) Sb-Cs - (4) Bialkali (Sb-Rb-Cs, Sb-K-Cs) - (5) High temperature, low noise bialkali (Sb-Na-K) - (6) Multialkali (Sb-Na-K-Cs) - (7) Ag-O-Cs - (8) GaAsP (Cs) - (9) GaAs (Cs) - (10) InGaAs (Cs) - (11) InP/InGaAsP(Cs), InP/InGaAs(Cs) - Transmission mode photocathodes - Reflection mode photocathodes
  • 4.1.2 Window materials - (1) MgF 2 crystal - (2) Sapphire - (3) Synthetic silica - (4) UV glass (UV-transmitting glass) - (5) Borosilicate glass
  • 4.1.3 Spectral response characteristics - (1) Radiant sensitivity - (2) Quantum efficiency - (3) Measurement and calculation of spectral response characteristics - (4) Spectral response range (short and long wavelength limits)
  • 4.1.4 Luminous sensitivity - (1) Cathode luminous sensitivity - (2) Anode luminous sensitivity - (3) Blue sensitivity index and red-to-white ratio
  • 4.1.5 Luminous sensitivity and spectral response
• 4.2 Basic Characteristics of Dynodes
  • 4.2.1 Dynode types and features - (1) Circular-cage type - (2) Box-and-grid type - (3) Linear-focused type - (4) Venetian blind type - (5) Mesh type - (6) MCP (Microchannel plate) - (7) Metal channel dynode - (8) Electron bombardment type
  • 4.2.2 Collection efficiency and gain (current amplification) - (1) Collection efficiency - (2) Gain (current amplification)
• 4.3 Characteristics of Photomultiplier Tubes
  • 4.3.1 Time characteristics.............................................................. - (1) Rise time, fall time and electron transit time - (2) TTS (transit time spread) - (3) CTTD (cathode transit time difference) - (4) CRT (coincident resolving time)
  • 4.3.2 Linearity - (1) Cathode linearity - (2) Anode linearity - (3) Linearity measurement
  • 4.3.3 Uniformity - (1) Spatial uniformity - (2) Angular response
  • 4.3.4 Stability - (1) Drift (time stability) and life characteristics - (2) Aging and warm-up
  • 4.3.5 Hysteresis - (1) Light hysteresis - (2) Voltage hysteresis - (3) Reducing the hysteresis
  • 4.3.6 Dark current - (1) Causes of dark current - (2) Expression of dark current
  • 4.3.7 Signal-to-noise ratio of photomultiplier tubes
  • 4.3.8 Afterpulsing - Types of afterpulses
  • 4.3.9 Polarized-light dependence
• References in Chapter - AND PERIPHERAL CIRCUITS CHAPTER 5 HOW TO USE PHOTOMULTIPLIER TUBES
• 5.1 Voltage-Divider Circuits
  • 5.1.1 Basic operation of voltage-divider circuits
  • 5.1.2 Anode grounding and cathode grounding
  • 5.1.3 Voltage-divider current and output linearity
    • (1) DC-operation output linearity and its countermeasures
    • (2) Pulse-operation output linearity and its countermeasures
  • 5.1.4 Voltage distribution in voltage-divider circuits
    • (1) Voltage distribution in the anode and latter stages
    • (2) Voltage distribution for the cathode and earlier stages
  • 5.1.5 Countermeasures for fast response circuits
  • 5.1.6 Practical fast response voltage-divider circuit
  • 5.1.7 High output linearity voltage-divider circuit (1)
  • 5.1.8 High output linearity voltage-divider circuit (2)
  • 5.1.9 Gating circuit
  • 5.1.10 Anode sensitivity adjustment circuits
  • 5.1.11 Precautions when fabricating a voltage-divider circuit
    • (1) Selecting the parts used for a voltage-divider circuit
    • (2) Precautions for mounting components
• 5.2 Selecting a High-Voltage Power Supply
• 5.3 Connection to an External Circuit
  • 5.3.1 Observing an output signal
  • 5.3.2 Influence of a coupling capacitor
  • 5.3.3 Current-to-voltage conversion for photomultiplier tube output
    • (1) Current-to-voltage conversion using load resistance
    • (2) Current-to-voltage conversion using an operational amplifier
    • (3) Charge-sensitive amplifier using an operational amplifier
  • 5.3.4 Output circuit for a fast response photomultiplier tube
• 5.4 Housing
  • 5.4.1 Light shield
  • 5.4.2 Electrostatic shield
  • 5.4.3 Magnetic shield
    • (1) Shielding factor of magnetic shield case and orientation of magnetic field
    • (2) Saturation characteristics
    • (3) Frequency characteristics
    • (4) Edge effect
    • (5) Photomultiplier tube magnetic characteristics and shielding effect
    • (6) Handling the magnetic shield case
• 5.5 Cooling
• References in Chapter
• CHAPTER 6 PHOTON COUNTING - 6.1 Analog and Digital (Photon Counting) Modes - 6.2 Principle of Photon Counting - 6.3 Operating Method and Characteristics of Photon Counting - (1) Circuit configuration - (2) Basic characteristics of photon counting
  • References in Chapter
• CHAPTER 7 SCINTILLATION COUNTING
  • 7.1 Scintillators and Photomultiplier Tubes
  • 7.2 Characteristics - (1) Energy resolution - (2) Relative pulse height - (3) Linearity - (4) Uniformity - (5) Stability - (6) Noise - (7) Plateau characteristic
  • References in Chapter
• CHAPTER 8 PHOTOMULTIPLIER TUBE MODULES....................
  • 8.1 What Are Photomultiplier Tube Modules?
  • 8.2 Characteristics of Power Supply Circuits - (1) Power supply circuits - (2) Ripple noise - (3) Settling time
  • 8.3 Current Output Type and Voltage Output Type - (1) Connection method - (2) Gain adjustment - (3) Current output type module - (4) Voltage output type module
  • 8.4 Photon Counting Head - (1) Output characteristics - (2) Counting sensitivity - (3) Count linearity - (4) Improving the count linearity - (5) Temperature characteristics - (6) Photon counting ASIC (Application Specific Integrated Circuit)
  • 8.5 Gate Function - (1) Gate noise - (2) Extinction ratio
  • 8.6 Built-in CPU and IF Type - (1) Photon counting type - (2) Charge amplifier and AD converter type
  • References in Chapter - PHOTOMULTIPLIER TUBES CHAPTER 9 POSITION SENSITIVE
  • 9.1 Multianode Photomultiplier Tubes
    • 9.1.1 Metal channel dynode type multianode photomultiplier tubes - (1) Structure - (2) Characteristics
    • 9.1.2 Multianode MCP-PMT
    • 9.1.3 Flat panel type multianode photomultiplier tubes - (1) Characteristics
  • 9.2 Center-of-Gravity Position Sensitive Photomultiplier Tubes - (cross-plate anodes) 9.2.1 Metal channel dynode type multianode photomultiplier tubes - (1) Structure - (2) Characteristics
    • 9.2.2 Grid type dynode photomultiplier tubes (Cross-wire anodes) - (1) Structure - (2) Characteristics
• CHAPTER 10 MCP-PMT
  • 10.1 Structure
    • 10.1.1 Structure of MCPs
    • 10.1.2 Structure of MCP-PMTs
    • 10.1.3 Voltage-divider circuit and housing structure
  • 10.2 Basic Characteristics of MCP-PMTs
    • 10.2.1 Gain characteristics
    • 10.2.2 Time characteristics............................................................ - (1) Rise/fall times - (2) Transit time - (3) TTS (transit time spread) - (4) Cathode transit time difference - (5) Time characteristics of various products
    • 10.2.3 Temperature characteristics and cooling
    • 10.2.4 Saturation characteristics - (1) Dead time - (2) Saturation in DC operation - (3) Pulse gain saturation characteristics (pulse linearity) - (4) Saturation gain characteristics in photon counting mode - (5) Count rate linearity in photon counting
    • 10.2.5 Magnetic characteristics
  • 10.3 Gated MCP-PMTs
  • 10.4 Multianode MCP-PMTs
  • References in Chapter
• CHAPTER 11 HPD (Hybrid Photo-Detector)
  • 11.1 Operating Principle of HPDs
  • 11.2 Comparison with Photomultiplier Tubes
  • 11.3 Various Characteristics of HPDs
    • 11.3.1 Multi-photoelectron resolution
    • 11.3.2 Gain characteristics and electron bombardment gain uniformity
    • 11.3.3 Time response characteristics
    • 11.3.4 Uniformity
    • 11.3.5 Light hysteresis characteristics
    • 11.3.6 Drift characteristics (short-term stability)
    • 11.3.7 Magnetic characteristics
    • 11.3.8 Temperature characteristics
  • 11.4 Connection Examples (R7110U Series) - transimpedance amp) 11.4.1 When handling DC signal (including connection to
    • 11.4.2 When handling pulse signal (via connection to charge amp)
  • References in Chapter
    • AND ION DETECTORS CHAPTER 12 ELECTRON MULTIPLIER TUBES
• 12.1 Structure
• 12.2 Characteristics
  • 12.2.1 Sensitivity to soft X-rays, VUV, electrons and ions
  • 12.2.2 Gain
  • 12.2.3 Dark current and noise
  • 12.2.4 Linearity
  • 12.2.5 Life characteristics
• References in Chapter - AND RELIABILITY CHAPTER 13 ENVIRONMENTAL RESISTANCE
• 13.1 Effects of Ambient Temperature
  • 13.1.1 Temperature characteristics - (1) Sensitivity - (2) Dark current
  • 13.1.2 High temperature photomultiplier tubes
  • 13.1.3 Storage temperature and cooling precautions
• 13.2 Effects of Humidity
  • 13.2.1 Operating humidity
  • 13.2.2 Storage humidity
• 13.3 Effects of External Magnetic Fields
  • 13.3.1 Magnetic characteristics
  • 13.3.2 Photomultiplier tubes for use in highly magnetic fields
  • 13.3.3 Magnetization
  • 13.3.4 Photomultiplier tubes made of nonmagnetic materials
• 13.4 Vibration and Shock
  • 13.4.1 Resistance to vibration and shock during non-operation
  • 13.4.2 Resistance to vibration and shock during operation (resonance)
  • 13.4.3 Testing methods and conditions
  • 13.4.4 Ruggedized photomultiplier tubes
• 13.5 Effects of Helium Gas
  • 13.6 Effects of Radiation
    • 13.6.1 Deterioration of window transmittance
    • 13.6.2 Glass scintillation
  • 13.7 Effects of Atmosphere
  • 13.8 Effects of External Electric Potential
    • 13.8.1 Experiment
    • 13.8.2 Taking corrective action
  • 13.9 Reliability
    • 13.9.1 Stability over time (life characteristic)
    • 13.9.2 Current stress and stability
    • 13.9.3 Reliability
      • (1) Failure mode
      • (2) Failure rate
      • (3) Mean life
      • (4) Reliability
    • 13.9.4 Reliability tests and criteria used by Hamamatsu Photonics
  • References in Chapter
• CHAPTER 14 APPLICATIONS
  • 14.1 Spectrophotometry
    • 14.1.1 Overview
    • 14.1.2 Specific applications
      • (1) UV, visible and infrared spectrophotometers
      • (2) Atomic absorption spectrophotometers
      • (3) Atomic emission spectrophotometers
      • (4) Fluorospectrophotometers
  • 14.2 Medical Equipment
    • 14.2.1 PET (Positron Emission Tomography)................................
    • 14.2.2 Gamma cameras
    • 14.2.3 Planar imaging device
    • 14.2.4 X-ray image diagnostic equipment
      • (1) X-ray phototimer
      • (2) Computed radiography (CR)
    • 14.2.5 In-vitro assay
      • (1) RIA (Radioimmunoassay) method
      • (2) Luminescent/fluorescent immunoassay
    • (3) Chemiluminescent immunoassay
• 14.3 Biotechnology
  • 14.3.1 Overview
  • 14.3.2 Application examples
    • (1) Flow cytometers
    • (2) Confocal laser microscopes
    • (3) DNA microarray scanners
    • (4) DNA sequencers
• 14.4 High-Energy Physics Experiments
  • 14.4.1 Overview
  • 14.4.2 Collision experiments
    • (1) Hodoscopes
    • (2) TOF counters
    • (3) Calorimeters
    • (4) Cherenkov counters
    • (5) Proton decay, neutrino observation experiments
• 14.5 Oil Well Logging
• 14.6 Environmental Measurement
  • 14.6.1 Overview
  • 14.6.2 Application examples
    • (1) Dust counters
    • (2) Laser radar (LIDAR)
    • (3) NOx analyzers
    • (4) SOx analyzers
• 14.7 Radiation Monitors
  • 14.7.1 Overview
  • 14.7.2 Application examples
    • (1) Handheld radiation monitor (pager)
    • (2) Door monitors
• 14.8 Industrial Measurement
  • 14.8.1 Overview
  • 14.8.2 Application examples
    • (1) Thickness gauges
    • (2) Laser scanners
• 14.9 Aerospace Applications
  • 14.9.1 Overview
  • 14.9.2 Application examples - (1) X-ray astronomy - (2) Ozone measurement (solar backscatter radiometer)
  • 14.10 Mass Spectrometry/Solid Surface Analysis
    • 14.10.1 Mass spectrometers
    • 14.10.2 Solid surface analyzers
  • References in Chapter
• Index

CHAPTER 1

INTRODUCTION

2 CHAPTER 1 INTRODUCTION

1.1 Overview of This Manual

The following provides a brief description of each chapter in this technical manual.

CHAPTER 1 INTRODUCTION

Before starting to describe the main subjects, this chapter explains basic photometric units used to measure or express properties of light such as wavelength and intensity. This chapter also describes the history of the development of photocathodes and photomultiplier tubes.

Chapter 2 Basic Principles of Photomultiplier Tubes

This chapter describes the basic operating principles and elements of photomultiplier tubes, including photoelectron emission, electron trajectories, electron multiplication by use of electron multipliers (dynodes), and anodes.

Chapter 3 Basic Operating Methods of Photomultiplier Tubes

This chapter is aimed at first-time photomultiplier tube users. It describes how to select and operate photo- multiplier tubes and how to process their signals.

4.3 Characteristics of Photomultiplier Tubes

Chapter 4 explains in detail the basic performance and various characteristics of photomultiplier tubes.

Chapter 5 How to Use Photomultiplier Tubes and Peripheral Circuits

This chapter describes how to use the basic circuits and accessories needed for correct operation of photo- multiplier tubes.

CHAPTER 6 PHOTON COUNTING

Chapter 6 describes the principle, method of use, characteristics and advantages of photon counting used for optical measurement at very low light levels where the absolute amount of light is extremely small.

CHAPTER 7 SCINTILLATION COUNTING

Chapter 7 explains scintillation counting with photomultiplier tubes for radiation measurement. It includes descriptions of characteristics, measurement methods, and typical examples of data.

CHAPTER 8 PHOTOMULTIPLIER TUBE MODULES....................

This chapter describes photomultiplier tube modules (PMT modules) developed to make photomultiplier tubes easier to use and also to expand their applications.

4 CHAPTER 1 INTRODUCTION

1.2 Photometric Units

Before starting to describe photomultiplier tubes and their characteristics, this section briefly discusses photometric units commonly used to measure the quantity of light. This section also explains the wavelength regions of light (spectral range) and the units to denote them, as well as the unit systems used to express light intensity. Since information included here is just an overview of major photometric units, please refer to specialty books for more details. 1) 2)

1.2.1 Spectral regions and units

Electromagnetic waves cover a very wide range from gamma rays up to millimeter waves. So-called "light" is a very narrow range of these electromagnetic waves. Table 1-1 shows how spectral regions are designated when light is classified by wavelength, along with the conversion diagram for light units. In general, what we usually refer to as light covers a range from 10^2 to 10^6 nanometers (nm) in wavelength. The spectral region between 350 and 750nm shown in the table is usually known as the visible region. The region with wavelengths shorter than the visible region is divided into near UV (shorter than 350nm), vacuum UV (shorter than 200nm) where air is absorbed, and extreme UV (shorter than 100nm). Even shorter wavelengths span into the region called soft X-rays (shorter than 10nm) and X- rays. In contrast, longer wavelengths beyond the visible region extend from near IR (750nm or up) to the infrared (several micrometers or up) and far IR (several tens of micrometers or up) regions.

Wavelength nm (Hz) (eV)

Vacuum UV region Ultraviolet region Visible region Near infrared region

X-ray Soft X-ray

Extreme UV region

Infrared region

Far infrared region

10 102

10

102

103 1

(^1010) - 4

(^1010) - 5

106 10 -

1016

1015

1014

1013

1012

200 350 750

Spectral Range Frequency Energy

Table 1-1: Spectral regions and unit conversions

1.2 Photometric Units 5

Light energy E (J) is given by the following equation (Eq. 1-1). E = hυ = h · c λ ······································································································· (Eq. 1-1) h υ c λ

: Planck's constant 6.626✕ 10 -34^ (J·s) : Frequency of light (Hz) : Velocity of light 3✕ 10 8 m/s : Wavelength (nm) Eq. 1-1 can be rewritten as Eq. 1-2, by substituting E in eV, wavelength in nanometers (nm) and constants h and c in Eq. 1-1. Here, 1 eV equals 1.6× 10 -19^ J.

E(ev) =^1240 λ ········································································································ (Eq. 1-2) From Eq. 1-2, it can be seen that light energy increases in proportion to the reciprocal of wavelength.

1.2.2 Units of light intensity

This section explains the units used to represent light intensity and their definitions. The radiant quantity of light or radiant flux is a pure physical quantity expressed in units of watts (J/S). In contrast, the photometric quantity of light or luminous flux is represented in lumens which correlate to the visual sensation of light. If the number of photons per second is n and the wavelength is λ, then Eq. 1-1 can be rewritten as Eq. 1- from the relation of W=J/S.

W = NE = Nhc λ ··································································································· (Eq. 1-3) Here, the following equation can be obtained by substituting specific values for the above equation. W = N^ ×^2 λ×^10 - The above equation shows the relation between the radiant power (W) of light and the number of photons (N), and will be helpful if you remember it. Table 1-2 shows comparisons of radiant units with photometric units (in brackets [ ]). Each unit is de- scribed in subsequent sections.

Quantity Unit Name Symbol Radiant flux [Luminous flux] watts [lumens] (^) W [lm] Radiant energy [Quantity of light] joules [lumen sec.] (^) J [lm·s] Irradiance [Illuminance] watts per square meter [lux] (^) W/m 2 [lx] Radiant emittance [Luminous emittance]

watts per square meter [lumens per square meter] W/m^ (^2) [lm/m (^2) ] watts per steradian [candelas] (^) W/sr [cd] Radiance [Luminance] watts per steradian square meter[candelas per square meter] [cd/mW/sr·m (^2) ]^2

Radiant intensity [Luminous intensity]

Table 1-2: Comparisons of radiant units with photometric units (shown in brackets [ ] )