Fluke 30-471 User Manual

Nuclear Associates 30-471

VeriDose

Solid-State Diode Detectors

Operators Manual

Fluke Biomedical

Radiation Management Services

6045 Cochran Road Cleveland, Ohio 44139

440.498.2564

120 Andrews Road Hicksville, New York 11801

516.870.0100

www.flukebiomedical.com/rms

Table Of Contents

Section 1: General Information................................................................................... 1-1

1.1 Introduction .................................................................................................. 1-1

1.2 Specifications............................................................................................... 1-2

1.3 Accessories ................................................................................................. 1-2

1.4 Calibration Technique.................................................................................. 1-2

1.5 Receiving Inspection.................................................................................... 1-3

1.6 Storage ........................................................................................................ 1-3

1.7 Routine Cleaning ......................................................................................... 1-3

1.8 Procedures, Warnings, and Cautions .......................................................... 1-3

Section 2: Operation.................................................................................................... 2-1

2.1 Operation ..................................................................................................... 2-1

2.2 Phonton Detectors ....................................................................................... 2-2

2.3 Electron Detectors ....................................................................................... 2-6

Section 3: Theory of Operation................................................................................... 3-1

3.1 Theory of Operation..................................................................................... 3-1

Section 4: Maintenance, Calibration and Troubleshooting...................................... 4-1

4.1 Maintenance ................................................................................................ 4-1

4.2 Calibration.................................................................................................... 4-1

4.3 Troubleshooting ........................................................................................... 4-1

Appendix A Drawings.....................................................................................................A-1

A.1 Drawings...................................................................................................... A-1

Appendix B: Radiation Damage ..................................................................................... B-1

B.1 Radiation Damage ....................................................................................... B-1

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General Information

Introduction

Section 1

General Information

This device is intended for use only by persons who have been trained in the proper interpretation of its readings and in the appropriate safety procedures to be followed in the presence of radiation.

These detectors are not designed, nor are they recommended for use in primary calibration.

WARNING

CAUTION

1.1 Introduction

The VeriDose Detectors, Models 30-471 through 30-475 and 30-471-8000 through 30-475-8000, are ntype diodes utilizing a p-n junction and are designed for use as radiation detection devices. These diodes are encased within a FDA approved polystyrene material. A low noise coaxial cable is used to connect the diode to an electrometer. In this configuration, these diodes provide enhanced sensitivity, instantaneous response time and are very rugged. With advantages such as large signal and fast response, these diodes are ideal for relative measurements in areas of steep dose gradients and relative absorbed dose in electron beam fields.

The Solid State Radiation Detector Diodes are constructed using a "parallel plate" geometry with planar electrodes opposing each other at a given spacing. This configuration has many advantages over the commonly used coaxial cylindrical geometry which have the electrodes being inner and outer shells.

The most obvious advantage is its superior construction and ease of orientation to the radiation beam. Unlike the cylindrical style diodes where the alignment of the diode's sensitive volume is critical in relationship to the radiation beam, the sensitive volume of the VeriDose Diode is the entire diode, which allows for a less stringent alignment to the radiation beam. The hemispherical shape also allows for easier attachment to the patient. The ideal orientation of the diode within the radiation beam is to have the beam perpendicular to the diode's horizontal axis. As long as the beam is wider than the diode, full collection of all ionization produced will occur regardless of the exact position in the active region. However, for ease of alignment within a radiation beam a raised X has been placed on top of the diode.

Figure 1-1. General View of the VeriDose Diode

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Nuclear Associates 30-471

Operators Manual

1.2 Specifications

Sensitivity:

Diameter:

Cable Length:

Output Polarity:

Weight:

Sensitive Volume:

Linearity:

Reproducibility:

Temp. Dependence:

Angular Dependence:

Rad Damage @10 kGy:

Operating Temp.:

Relative Humidity:

1.5 nC/cGy Phonton: 12 mm Diameter

Electron: 11 mm Diameter 2 meters

pos/neg

42 gm

0.25 mm

2.25%

0.2%

< 0.5% /°C

Refer to the graphs on page 18 - 25

< 15%

10° C to 40° C (50° F to 104° F)

5 to 95%, non-condensing

1.3 Accessories

Part Number Description

VeriDose QC (37-705-5000)

Diode Detector Holder (37-492-1000)

Calibration Fixture (37-705-4000)

Extension Cable (88-490)

Dual purpose acrylic phantom, daily QA, flatness/symmetry & depth dose

Acrylic, 5-slot, wall mount

Acrylic, 5-slot

10 meter low noise coaxial cable

1.4 Calibration Technique

The VeriDose diode detectors are part of a dose monitoring system. In order to obtain accurate results, the detectors must be used with a suitable patient dose-monitoring device. The VeriDose V, available from Fluke Biomedical, Radiation Management Services is a 5-channel dose monitor designed specifically for use with this type of detector. A calibration fixture is available to hold the detectors in a fixed, reproducible geometry during the calibration process. For optimum performance, the detector must be used within the energy range for which it was designed. Since the detectors are designed with an internal build-up cap, additional build-up is not required.

It is recommended that the system be calibrated under clinical conditions at which the detectors will be normally used. Since the calibration process will associate a particular detector to a specific channel on the dose-monitoring device, it is necessary to exercise caution when reconnecting the detectors for subsequent measurements. Each detector must be connected to the channel to which it was calibrated.

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General Information

Calibration Technique

The detectors must be positioned in close proximity to the isocenter using the optional calibration fixture or an alternative method to obtain a uniform dose. A typical exposure of 100-200 cGy at a dose rate of 100-300 cGy/min is adequate for calibration. Refer to the calibration section of the appropriate operator’s manual for the dose-monitoring device for a complete description of the adjustment procedure. Upon completion of the calibration process, several additional exposures should be made in the normal measurement mode of the dose monitor in order to verify the calibration.

1.5 Receiving Inspection

Upon receipt of the diodes:

1. Inspect the carton(s) and contents for damage. If damage is evident, file a claim with the carrier and contact Fluke Biomedical, Radiation Management Services at 440.248.9300.

2. Remove the contents from the packing material and visually inspect the unit for damage.

3. Verify that all items on the packing list have been received and are in good condition.

1.6 Storage

If the diodes are to be stored prior to use, pack them in the original container, if possible, and store in an environment free of corrosive materials, fluctuations in temperature and humidity, and vibration and shock.

1.7 Routine Cleaning

The VeriDose diodes should be kept clean and free from dirt and contamination. The unit may be cleaned by wiping with a damp cloth, using any commercially available cleaning or decontaminating agent.

1.8 Procedures, Warnings, and Cautions

The equipment described in this manual is intended to be used for the detection and measurement of ionizing radiation. It should be used only by persons who have been trained in the proper interpretation of its readings and the appropriate safety procedures to be followed in the presence of radiation.

Although the equipment described in this manual is designed and manufactured in compliance with all applicable safety standards, certain hazards are inherent in the use of electronic and radiometric equipment.

WARNINGS and CAUTIONS are presented throughout this document to alert the user to potentially hazardous situations. A WARNING is a precautionary message preceding an operation which has the potential to cause personal injury or death. A CAUTION is a precautionary message preceding an operation which has the potential to cause permanent damage to the equipment and/or loss of data. Failure to comply with WARNINGS and CAUTIONS is at the user's own risk and is sufficient cause to terminate the warranty agreement between Fluke Biomedical and the customer.

Adequate warnings are included in this manual and on the product itself to cover hazards that may be encountered in normal use and servicing of this equipment. No other procedures are warranted by Fluke Biomedical. It shall be the owner's or user's responsibility to see to it that the procedures described here are meticulously followed, and especially that WARNINGS and CAUTIONS are heeded. Failure on the part of the owner or user in any way to follow the prescribed procedures shall absolve Fluke Biomedical and its agents from any resulting liability.

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Nuclear Associates 30-471

Operators Manual

Indicated battery and other operational tests must be performed prior to each use to assure that the instrument is functioning properly. If applicable, failure to conduct periodic performance tests in accordance with ANSI N323-l978 (R1983) Radiation Detection Instrumentation Test and Calibration, paragraphs 4.6 and 5.4. and to keep records thereof in accordance with paragraph 4.5 of the same standard, could result in erroneous readings or potential danger. ANSI N323-1978 becomes, by this reference, a part of this operating procedure.

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