Ludlum Measurements 44-9 Manuel utilisateur

LUDLUM MODEL 44-9

ALPHA, BETA, GAMMA DETECTOR

February 2010

Serial Number PR090405 and Succeeding

Serial Numbers

LUDLUM MODEL 44-9

ALPHA, BETA, GAMMA DETECTOR

February 2010

Serial Number PR090405 and Succeeding

Serial Numbers

LUDLUM MEASUREMENTS, INC.

501 OAK STREET, P.O. BOX 810

SWEETWATER, TEXAS 79556

325-235-5494, FAX: 325-235-4672

Model 44-9 Alpha, Beta and Gamma Detector

Ludlum Measurements, Inc. February 2010

Table of Contents

Int roduction 1

U npa c k ing a nd Re pa c k ing 2

Spe c ific a t ions 2

Ope ra ting Proc e dure s 3

T ube Re pla c e m e nt 4

Pa rts List 6

Dra w ings a nd Dia gra m s 7

Mode l 44-9 Pa nc a k e Probe , Dra w ing 2 × 2 0 6 7

Ga m m a Ene rgy Re sponse 8

Bet a Efficienc ies 8

Model 44-9 Alpha, Beta and Gamma Detector

Ludlum Measurements, Inc. Page 1 February 2010

Introduction

The Ludlum Model 44-9 GM (Geiger-Mueller) Detector

detects alpha, beta, and gamma radiation. Its size and shape

(pancake) provide easy handling for surveying or personnel

monitoring. The detector is energy dependant, over-responding

by a factor of 6 in the 60 keV to 100 keV range when

normalized to 137Cs.

The thin mica window is protected by a 79% open stainless

steel screen. The GM tube can be easily removed for

replacement if necessary.

This detector operates between 850-1000 volts, with a

recommendation from the tube manufacturer of approximately

900 Vdc. Recommended instrument input sensitivity is

approximately 30 mV or higher to prevent the detector from

double pulsing (where the detector “counts” a single pulse

from the instrument multiple times.)

Ca ution!

The GM tube face can rupture above 8000 feet in

altitude. When transporting this detector by air, use an

airtight container in order to avoid sudden atmospheric

changes resulting in tube failure.

The Ludlum Model 44-9 will operate with any Ludlum

instruments or equivalent instruments that provide 900 Vdc

and an input sensitivity of approximately 30 mV or higher.

Model 44-9 Alpha, Beta and Gamma Detector

Ludlum Measurements, Inc. Page 2 February 2010

Unpacking and Repacking

Remove the calibration certificate or detector functional check

certificate and place it in a secure location. Remove the

detector(s) and accessories (if applicable) and ensure that all

items listed on the packing list are in the carton. If multiple

detectors are included, refer to the calibration certificates for

serial number (SN) matches. The Model 44-9 serial number is

located on the detectors’ bottom plate.

To return an instrument or detector for repair or calibration,

provide sufficient packing material to prevent damage during

shipment (see “Caution!” in Introduction section) and affix

appropriate warning labels to promote careful handling. The

following items and information should also be included to

ensure quick turnaround time of your equipment.

•instrument(s) and related cable(s)

•brief description as to the reason for return

•description of service requested

•return shipping address

•customer name and telephone number

Specifications

Efficiency (4π geometry): typically 5% for 14C; 22% for

90Sr/90Y; 19% for 99Tc; 32% for 32P; 15% for 239Pu;

≤ 1% for 99mTc

Se nsitivit y: typically 3300 cpm per mR/hr (137 Cs gamma)

Energy Response : energy dependent (please see graphs on

page 7)

Ba ck ground: 60 cpm

De ad T im e: typically 80 µs

Window: 1.7 ±0.3 mg/cm2mica

Model 44-9 Alpha, Beta and Gamma Detector

Ludlum Measurements, Inc. Page 3 February 2010

Window Area: active is 15 cm2; open is 12 cm2

De te ct or: pancake-type halogen quenched GM

De te ct or Operating Volt age: 900 Vdc

Com pa tible I nstruments: general purpose survey meters,

ratemeters, and scalers.

Conne ct or: series ˝C˝(others available)

Construc tion: aluminum housing with beige powder-coat

finish; stainless steel protective screen (79% open)

Te mperat ure Range: -15 to 50 °C (5 to 122 °F); may be

certified for -40 to 65 °C (-40 to 150 °F)

Size : 4.6 x 6.9 x 27.2 cm (1.8 x 2.7 x 10.7 in.) (H x W x L)

We ight: 0.5 kg (1 lb)

Operating Procedures

CONNECTING TO AN INSTRUMENT

Connect one end of the cable provided to the

detector by firmly pushing the connector

together while twisting clockwise a quarter of a

turn until latched. Repeat the process in the

same manner with the other end of the cable

and the instrument.

TESTING THE DETECTOR

1. Ensure that the instrument high voltage (HV) is at the

proper setting for the detector (900 volts)

Model 44-9 Alpha, Beta and Gamma Detector

Ludlum Measurements, Inc. Page 4 February 2010

2. Connect the detector to the instrument and check for a

proper background reading (typically 25-50 cpm at 8-15

µR/hr).

3. Expose the detector to a check source and verify that the

instrument indicates within 20% of the check source

reading from the last calibration. Alternatively, expose the

detector to a source of known value and verify that the

detector detects greater than or equal to the efficiency

listed in the specification section of this manual.

4. Instruments and detectors that meet these criteria are

ready for use. Failure to meet these criteria may indicate a

malfunction in the detector.

Tube Replacement

Refer to drawing 2 × 206 located on page 7 of this manual to

assist with replacement.

1. Remove the back plate by removing the three screws.

2. Loosen the three set screws on the side of the tube

housing.

3. Remove the old tube from the detector housing.

4. Remove the anode clip from the old tube.

5. Push the clip onto the anode housing.

Note :

Do not over-flex the wire when installing the clip, as

damage may occur.

Model 44-9 Alpha, Beta and Gamma Detector

Ludlum Measurements, Inc. Page 5 February 2010

Ca ution!

The mica window of this tube is extremely thin and

fragile. There is also a thin layer of material to prevent

UV interference. This material may come off if touched,

causing the detector to malfunction. DO NOT TOUCH

6. Carefully install the tube with the window facing down in

the housing.

7. Ensure the tube is flush against the screen and tighten the

set screws.

8. Replace the back plate and retaining screws.

9. Recalibrate the instrument and detector before use.

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