Dosimeter : Three-element BARC CaSO₄ (Dy) PTFE disc dosimeter badge

Light Measurement System : Photo-multiplier tube (EMI 9125A -bialkali) Light measuring system (LMS)

Dark current : Dark current is 1 Sv (CaSO₄) equivalent with software-based sampling & subtraction

Heating Method : Hot gas (N₂) heating

Heating Cycle : The temperature is raised to 280°C in 8 sec and clamped at 280°C

Dose Range
50µSv – 5Sv (Gamma) and
100µSv – 5Sv (Beta)

Dose Threshold : <50µSv

Readout time : 100 sec. per badge

Residual Signal : <10% of reading

Facilities Available : Automatic sensing of ID numbers, editing of calibration factor etc. Storage of dose and glow curve data of badges in floppy/hard disk. Motorised driver assembly for automatic feeding of 50 dosimeter cards loaded in a magazine.

Software : IBM PC compatible menu driven in WINDOWS based software for transfer of data to user defined file, storage and display of glow curves, computations of dose and generation of dose reports.

Temperature Monitoring : Chromel Alumel thermocouple in hot gas stream. External temperature monitoring output at the back panel.

Range Selection : Automatic from 9.999µSv to 5.000Sv

Calibration : Coarse adjustment by varying the EHT through a potentiometer in the EHT circuit; fine through software.

Safeguards : Heater/Gas flow failure.: The heater and gas flow are checked for failure in every dosimeter readout cycle. In the event of failure of heater or gas flow the readout is terminated and a message indicating heater / gas flow failure is flashed on the PC monitor.
Mechanical Failure : Any mechanical failure during readout cycle is sensed using a timeout watchdog programme and the cycle is terminated with an option for the user to restart the cycle. EHT or the input circuit (I-F converter) is sensed and reading cycle is terminated in case of failure.

Nominal Power Supply
Power supply : 230V, 50Hz :
Power requirements : 500 VA (max including PC)

PC Requirements : IBM Pentium IV or upward compatible, with FDD and HDD drives, VGA monitor, Serial and parallel ports with Windows XP operating system.

Applications : Personnel Monitoring of radiation workers in Nuclear power stations, Isotope laboratories, Industrial radigraphy installations, diagnostic & therapeutic radiology centres, etc.

The software is a GUI interactive software. These options are ‘ICONS’ in tool bar and drop down menus in menu bar. These are the software features as given below.

On opening this software normally 1,3-6, 8-15 and 24 icons are enabled. The remaining icons are desabled. These desabled icons are enabled on opening the glow curve file.

Technical Data

Three CaSO₄ : Dy Teflon TLD discs are mechanically clipped on an Alluminium plate. An asymmetric “V” cut is provided in the card to ensure its loading in the plastic cassette as well in heater drawer / magazine of TLD reader in only one orientation. Alluminium card should be uniformly Nikel plated or buffed, having plating thickness of about 10 micron.

Dimensions of TLD card :
Dimensions of A1 card : 52.5 mm X 30.0 mm X 1.0 mm
Dimensions of hole on A1 Plate : 12.0 mm dia
Dimensions of TLD Disc : 13.3 mm dia

Characteristics of CaSO₄ : Dy Teflon TLD disc
Ratio of CaSO₄ : Dy and Teflon : 1: 3
Effective Atomic Number (Z) : 15.1
Density of the TLD Disc : 2.52 g/cm3
Softening Point of Teflon : 330^o C
Main Glow Peak Temperature : 230^o C
Sensitivity of TLD Disc : About 30-40 times more than LiF TLD-100
Fading : 2-3% in six months
Climactic Effect : Negligible
Effect of Sunlight : Negligible when covered by paper wrapper & polythene pouch and loaded in the badge
Useful Linear Dose Range : 0.10 mSV to 20 SV (linearity within + 10%)
Reusability : 20 cycles
Beta Response : 60% of 60Co gammas for Nat.U (effective energy 0.8Mev)
Thermal Neutron Response : 60Co gamma ray equivalent to 2.4 mGy per 1010 n/cm2
Fast Neutron Response : Negligible

Technical Data

• Three well-defined regions in the plastic cassette / holder corresponding to three TLD discs of the TLD card.

i. Disc D1- sandwiched between a pair of filter combination of 1.0mm thick Cu (Copper filter nearer to the disc).
ii. Disc D2- sandwitched between a pair of 1.6mm thick (180mg/cm2) plastic filters and
iii. Disc D3- under a circular open window.

• The asymmetric “V” cut of the card permits its loading in the plastic cassette in only one orientation and ensures proper positioning of three disc.

• For identification purposes, photograph of the user could also be permanently fixed on the central transparent region of the badge.

• There are two types of TLD badges/ cassettes in use namely,

1. Chest Badge for whole body monitoring and
2. Wrist Badge for extremity dosimetry

Though the dosimeter and design of both TLD badges are same, they have different attachment (clip/strap) for wearing purpose depending on their use.

TLD CASSETTE DIMENSIONS

In this design of the TLD cassette, dimension of some of the filters was altered and crocodile clip was replaced by a smaller size clip. The cassette was made of ABS plastic (white) and filters were embedded into the plastic body.

Dimensions :
Main Body :
Cu filter (rectangular) : 32 mm x 16 mm x 1mm
A1 filter (circular) : 13.6 mm x thickness – 0.6 mm
Plastic filter (rectangular) : 30.5 mm x 21 mm x 1.6 mm
Open window : Dia – 14.5 mm

Slider part :
Cu filter (rectangular) : Dia – 15.6 mm, x thickness – 1 mm
A1 filter (circular) : Dia – 12.6 mm, x thickness – 0.6 mm
Plastic filter (rectangular) : Dia – 25 mm, x thickness – 1.5 mm
Open window : Dia – 13.5 mm

SPECIFICATIONS OF HOT AIR ANNEALING OVEN

Working Chamber Size : 12” x 12” x 12” (APPROX)

Working Temperature : From ambient to 350^oC / 400^oC

Temperature Accuracy : + / - 1^oC

Temperature Indication & Control : By Automatic Electronic Digital Display Controller cum Indicator with Thermocouple.

Time Setting : By an Electronic Digital Timer of 0-1 minutes with associate logic circuit for setting the period of annealing and automatically putting off the heater and even after the set period.

Air Circulation System : For maximum uniformity of temperature inside the working chamber, air circulating system is provided by means of a meter driven fan.

Heaters : Heaters are made out of best quality Nichrome Wire insulated with refractory runners and enclosed in stainless steel sheet and fitted to the sides of the Oven.

Construction of Oven Body : The Oven body will be of triple walled construction with inner and middle wall made out of S.S. 304 material and outer wall made out of C.R.C.A. sheets duly painted or power coated.

Door : An insulated hinged side swinging type double walled door (inner S.S. 304 and outer H.S.) with asbestos gasket, ball catch lock and handle provided for easy and effortless closing & opening of door.

Insulation : High grade ceramic fibre blanket insulation is provided on all the six sides of the Oven.

Power Rating : 2.5 K.W.

Input Supply : Single Phase AC, 230 Volts

Trays/Shelves : 2 Nos. Stainless Steel trays provided.