Ludlum Measurements 44-9 User manual

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: [phone]

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.