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Model 2241-4

Neutron Dose Survey Meter

Part Number: 48-2973

Features

22.9 cm (9 in.) Moderated Neutron Detector
Range: 0 to 100 mSv/h (0 to 10,000 mrem/hr)
Gamma Rejection up to 0.1 Sv/h (10 R/hr)
Ratemeter with Built-in Scaler Function
Autoranging
Independent Adjustable Alarms for Ratemeter & Scaler Modes
RS-232 Connection

The Model 2241-4 is a portable neutron REM meter. This instrument combines Ludlum's microprocessor-based digital Scaler-Ratemeter Model 2241 electronics with a Model 42-31H Neutron Detector. This system is sensitive to neutrons from thermal to 12 MeV with a response approximating the inverse RPG curve for neutron dose.

Data is presented on a four-digit LCD with a moving decimal point. Two additional digits are employed for the Scaler mode. A three-position switch labeled Off/Ratemeter/Scaler selects the desired operating mode for the instrument. Other controls include Audio On/Off switch, Fast/Slow Response switch, LCD Backlight pushbutton, Count Reset pushbutton, and Scaler Count/Stop pushbutton.

This instrument incorporates independent adjustable alarms for the ratemeter and scaler operating modes. Audible alarms may be silenced (acknowledged) by depressing the RESET switch. The scaler count time, alarm values, and backlight on time are pre-programed values. This instrument can be programmed via its RS-232 port, which can also be used to output readings at two-second intervals.

Medical Application

NCRP Report #151 redefines the need to evaluate not only new Linac installations but also equipment that has been upgraded for higher energies and broader capabilities, like IMRT and rotational beam systems, which may be beyond what original shielding designs had recommended.

Specifications

Detector	³He tube (LND 25185 or equivalent)
Moderator	22.9 cm (9 in.) diameter cadmium-loaded polyethylene sphere
Measurement Range	0 to 100 mSv/h (0 to 10,000 mrem/hr)
Sensitivity (moderated ²⁵²Cf)	Typically 10 cpm per µSv/h (100 cpm per mrem/hr) (bare AmBe neutrons)
Energy Response	Provides appropriate inverse RPG curve for neutrons from thermal through 7 MeV, provides response up to 12 MeV
Gamma Rejection (¹³⁷Cs)	< 10 cpm through 0.1 Sv/h (10 R/hr)
Display	4-digit LCD with 1.3 cm (0.5 in.) height, plus two 0.5 cm (0.2 in.) digits used for overflow counter (scaler mode) and exponential powers (parameter setup)
Controls	Off / Ratemeter / Scaler three-position operation switch Audio on/off switch Fast/Slow response switch LCD backlight pushbutton Count reset pushbutton Scaler count pushbutton on the handle
Alert / Alarm	Pre-programmed alarms for ratemeter and scaler modes
Audio	Built-in audio speaker with audio on/off switch, greater than 60 dB at 0.6 m (2 ft)
Scaler Time	Adjustable from 1 to 999,999 s, can display seconds or minutes
Operating Voltage	Approximately 1200 Vdc
Input Sensitivity	-2 mV
Temperature Range	-20 to 50 °C (-4 to 122 °F)
Environmental Rating	IP rating of 53
Power	Two each “D” cell batteries housed in an externally accessible sealed compartment
Battery Life	Typically 200 hours, low battery symbol alert (instrument will operate for approximately 24 hours after symbol first appears)
Detector Connector	Series “C” (others available)
RS-232	“D” type connector, used for programming instrument and outputting data at two-second intervals, baud rate from 150 to 19,200 bps
Size	Meter (H x W x L): 16.5 x 8.9 x 21.6 cm (6.5 x 3.5 x 8.5 in.) Detector (H x W x D): 26.2 x 22.9 x 22.9 cm (10.3 × 9.0 × 9.0 in.), including brackets
Weight	Meter: 1.6 kg (3.5 lb) including batteries Detector: 6.56 kg (14.5 lb)

Options

Option	Description	Part Number
Case for Neutron Meters	Rugged transport and storage case.	2310377
Case for Neutron Meters	Rugged transport and storage case. Has wheels and extendable handle.	2311487

Replacement Parts

Description	Part Number
RS-232 Cable (9-pin)	8303-458
RS-232 Cable (25-pin)	8303-459
Meter Bezel	4408-051
Digital Display	5408-259
Rolled Handle	4408-075
Flat Handle	4408-090