Personnel Gamma Portal Monitor - Model 53
Introduction

The Model 53 Gamma Personnel Portal detects gamma radiation in or on personnel passing through the portal from either direction. This highly sensitive portal uses eight large plastic scintillation detectors. Shielding is accomplished with either the standard 2.5 cm (1 in.) or optional 5.1 cm (2 in.) thickness of lead. A user-friendly interface guides personnel through the portal monitor via automated voice prompts, and is accompanied with 22.9 cm (9 in.) color LCD articulating screens presenting the instrument readiness and status at the ingress and egress. Alarms are manifested both audibly and visually, and can be silenced and acknowledged via control buttons located on either side of the instrument.

Three statistical counting modes are available to maximize throughput, maximize sensitivity, or fix the count time. Several modifiable parameters adjust the alarm set point, including the false alarm probability, detection probability, background sigma coefficient (KB), and the composite sigma coefficient (KS+B). Fast alarm and clean options provide the ability to quickly determine if personnel are contaminated or clean before the entire count cycle has ended.

There are also four user modes to choose from that include a walk-through mode, a pause mode, a pause-and-turn mode, and a front-and-back mode. Voice prompts may be customized in any language for each of these modes. These prompts can, for example, dictate in-house procedures to follow. Instrument technicians have password-protected access to set up the instrument, and to the advanced automated routines for calibrating and verifying operation.

Easily accessible USB ports facilitate connecting a keyboard to implement changes, input user ID, or upload revised software. The system also includes an Ethernet link. Ludlum's optional Universal Network Software can be used to log instrument status, user activity, and other information from one or more  instruments connected to the network. This software broadcasts emails whenever radiological alarms or instrument failures occur, and has the ability to capture images from network cameras that can be stored along with the user ID (if implemented).

A unique feature is an optional weight scale that assesses the weight of the individual passing through the portal and then assigns an appropriate transmission factor for a more accurate gamma measurement. Other options include an additional 2.5 cm (1 in.) of lead shielding, a second alarm/light stack, and the Universal network software.
 
Another version of this personnel portal is the Model 53B (Part Number 48-3925), which detects beta radiation in addition to gamma. The detector access doors on the sides and on top have openings with metalized polyester windows to permit beta transmission. The window thickness is 1.2 mg/cm². Beta efficiency for 90Sr/Y is ≥7% at 7.6 cm (3 in.) from the side and top detectors. It is 0% on the foot detectors where there are no openings. For more information see the Model 53B Data Sheet.