Ludlum Measurements 43-5 User manual

LUDLUM MODEL 43-5
ALPHA SCINTILLATOR
February 2021

LUDLUM MODEL 43-5
ALPHA SCINTILLATOR
February 2021

STATEMENT OF WARRANTY
Ludlum Measurements, Inc. warrants the products covered in this manual to be free of
defects due to workmanship, material, and design for a period of twelve months from
the date of delivery. The calibration of a product is warranted to be within its specified
accuracy limits at the time of shipment. In the event of instrument failure, notify
Ludlum Measurements to determine if repair, recalibration, or replacement is required.
This warranty excludes the replacement of photomultiplier tubes, G-M and proportional
tubes, and scintillation crystals which are broken due to excessive physical abuse or
used for purposes other than intended.
There are no warranties, express or implied, including without limitation any implied
warranty of merchantability or fitness, which extend beyond the description of the face
there of. If the product does not perform as warranted herein, purchaser’s sole remedy
shall be repair or replacement, at the option of Ludlum Measurements. In no event will
Ludlum Measurements be liable for damages, lost revenue, lost wages, or any other
incidental or consequential damages, arising from the purchase, use, or inability to use
product.
RETURN OF GOODS TO MANUFACTURER
If equipment needs to be returned to Ludlum Measurements, Inc. for repair or calibration, please send
to the address below. All shipments should include documentation containing return shipping address,
customer name, telephone number, description of service requested, and all other necessary
information. Your cooperation will expedite the return of your equipment.
LUDLUM MEASUREMENTS, INC.
ATTN: REPAIR DEPARTMENT
501 OAK STREET
SWEETWATER, TX 79556
800-622-0828 325-235-5494
FAX [phone]

TABLE OF CONTENTS
1. GENERAL......................................................................................................................1
2. SPECIFICATIONS.........................................................................................................1
3. MAINTENANCE...........................................................................................................1
3.1 Repair of Probe Face..........................................................................................1
3.2 Replacement of PMT.........................................................................................2
REPLACEMENT PARTS LIST................................................................................................3
1.5-inch Tube Socket, Drawing 2 x 286 ........................................................................3
DRAWINGS AND DIAGRAMS...............................................................................................5
Model 43-5 Assembly View, Drawing 77 x 23
Model 43-5 Overall with Window, Drawing 77 x 23A
1.5-inchTube Socket, Drawing 2 x 317
1.5-inch Tube Socket Component Outlines, Drawing 2 x 318

Model 43-5 Alpha Scintillator
February 2021
page 1
1. GENERAL
The Model 43-5 Alpha Scintillator is a detector
(probe) designed for alpha radiation survey
when used with general purpose survey meters,
ratemeters, and scaler instruments. It utilizes a
zinc sulfide scintillation crystal doped with
silver [ZnS(Ag)] and a 3.8 cm (1.5 in.)
diameter magnetically shielded photomultiplier
tube (PMT).
The welded detector body is fabricated from
16-gauge (1/16 inch) aluminum alloy and
painted with a beige powder-coat finish. The
window protective screen is made of 0.13 cm
(0.05 in.) thick unpainted aluminum alloy, and
the window is aluminized metallized polyester,
typically 0.8 mg/cm2thick. When intended for
outdoor use, an extra layer of metallized
polyester is recommended (total of 1.2 mg/cm2
thickness).
A plastic protective cover is provided for
protection of the detector face against puncture
of the metallized polyester when the detector is
not in use. Pinholes in the window will cause
light leaks and malfunction of the detector.
2. SPECIFICATIONS
WINDOW: typically 0.8 mg/cm2aluminized
metallized polyester (1.2 mg/cm2for outdoor
use)
WINDOW AREA: 52 cm2(8.1 in2) open, 79
cm2(12.2 in2) active
EFFICIENCY: 13% of 4emission with
239Pu source in contact with probe protective
screen
BACKGROUND: 3 cpm or less
SCINTILLATOR: ZnS (Ag)
TUBE: 3.8 cm (1.5 in.) diameter
DYNODE STRING RESISTANCE: 100
megohm
OPERATING VOLTAGE: 500-1200
volts
CONNECTOR: Series “C” (others
available)
SIZE: 7.6 x 6.4 x 34.3 cm (3 x 2.5 x 13.5
in.) (H x W x L)
WEIGHT: 0.9 kg (2 lb)
3. MAINTENANCE
Normally, causes of malfunction of the Model
43-5 are due to either light holes in the thin
metallized polyester or a defective multiplier
tube. The malfunction caused by light holes
gives an increase in background noise up to
complete saturation where the instrument may
indicate zero count. If the instrument indicates
zero count, reduce the high voltage and cover
probe face with an opaque material. By
movement of the opaque material, a light leak
should be discernible.
3.1 Repair of Probe Face
To repair the face of the probe, perform the
following steps: (Refer to Drawing 77 x 23 for
assembly view.)

M43-5 Alpha Scintillator
February 2021
page 2
1. Remove protective window frame.
2. Remove window with metallized
polyester assembly from scintillation
retainer face.
3. Remove aluminized metallized
polyester from window screen and
clean off old glue from screen.
4. Inspect silicone gasket and replace if
damaged.
5. Inspect scintillation retainer face for a
complete coating of ZnS. Re-coat, if
necessary.
6. Reglue two layers of 0.4 mg/cm2
aluminized metallized polyester to
window screen, placing glue only on
the outer edge of the screen.
**CAUTION**:
The thin metallized polyester film is
very susceptible to puncture. Extreme
care should be exercised while gluing
the aluminum metallized polyester to
the window screen and when
reinstalling window with metallized
polyetser assembly to the face of the
probe.
7. Reinstall window with meatllized
polyester to face of probe.
Malfunctions caused by the tube, such as a zero
count, intermittent or a very reduced count,
may occur. After thoroughly checking for a
light leak, replacement of the tube may be
necessary. After removing the tube from the
probe body, check the front of the tube face. A
tube that has become defective may show clear
through the face, instead of the dark amber
color.
3.2 Replacement of PMT
To replace the PMT, perform the following
steps: (See Drawing 77 x 23.)
NOTE: If the replacement is for an original
“based” tube (Part No. 01-5001), refer to
instructions included in the installation kit.
NOTE: When needed, use thermal strippers
to strip the white Teflon high-voltage signal
wire to prevent damaging the wire.
1. Unfasten connector end cap (removing
four screws).
2. Slowly remove connector end cap and
pull out as far as wires will allow.
3. Remove (desolder) ground and high-
voltage wires from connector end cap.
4. Remove sponges.
5. Remove photomultiplier tube assembly
(including circuit board).
6. Unplug ground and high-voltage wires
from tube circuit board.
7. Remove metallic shield.
8. Slide the metallic shield over the new
tube and tape to tube.
9. Plug in ground and high-voltage wires
to appropriate connectors.
10. Place tube assembly into handle.
11. Install sponges.
12. Reconnect (solder) the high-voltage
and ground wires to connector end cap.
13. Install connector end cap to complete
final assembly.

Model 43-5 Alpha Scintillator
February 2021
page 3
REPLACEMENT PARTS LIST
Ref. No. Description Part No.
UNIT Completely Assembled 47-1521
Model 43-5 Probe
Part No. Description Qty.
4002-510 PM TUBE-ADIT 1 EA.
40-4006 TUBE SHIELD 1 EA.
40-4111 WINDOW W/MYLAR 1 EA.
03-5412 DOUBLE-SIDED TAPE
14-5431 ZINC SULFIDE (SOLD BY OZ.)
13-7751 "C" CONNECTOR UG706/U 1 EA.
03-5432 COUPLING SILICONE GREASE
17-8811 4-40 X 3/16 FH SCREW 4 EA.
17-8511 4-40 X 5/16 BH SCREW 4 EA.
21-9362 WHITE TEFLON WIRE 3-inch
21-9432 #26 BLACK WIRE 3-inch
22-9631 SILICONE CORD- 0.139 GASKET
2077-023 COMPLETE BODY ASSY. W/WINDOW FRAME 1 EA.
7002-505 CONNECTOR END CAP 1 EA.
*40-4049 ADJUSTABLE GAIN END CAP (OPTIONAL)
16-8317 O-RING-2-029 1 EA.
7002-029-04 PLEXIGLASS SPACER 1 EA.
7002-029-05 SPONGE 4 EA.
7085-064 CONNECTOR WRENCH (FOR "C" CONN.)
7077-027 TUBE RETAINER 1 EA.
7077-030 ACRYLIC RETAINER 1 EA..
1.5 Inch Tube Socket, Drawing 2 x 317
Ref. No. Description Part No.
BOARD Completely Assembled 5002-502
1.5 inch Tube Socket
CAPACITORS
C1 0.01µF, 2kV, C 04-5525
RESISTORS
R1 10 MEG 10-7106
R2 1 MEG 12-7964

M43-5 Alpha Scintillator
February 2021
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Ref. No. Description Part No.
R3-R6 10 MEG 10-7106
R11 10 MEG 10-7106
R101-R104 10 MEG 10-7106
R111 10 MEG 10-7106
MISCELLANEOUS
12 ea. Contact-003-1381-003 01-5245
*OPTIONAL
Ref. No. Description Part No.
BOARD* Completely Assembled 5209-019
Gain Control
CAPACITORS
C1 0.0047µF, 3kV, C 04-5547
RESISTORS
R1 100k TRIMMER POT 09-6813
MISCELLANEOUS
Cloverleaf-011-6809-000-599 18-8771
*Note: For units with Gain Control only.

Model 43-5 Alpha Scintillator
February 2021
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DRAWINGS AND DIAGRAMS
Model 43-5 Assembly View, Drawing 77 x 23
Model 43-5 Overall with Window, Drawing 77 x 23A
1.5 Inch Tube Socket Board, Drawing 2 x 317
1.5 InchTube Socket Component Outlines, Drawing 2 x 318