Radiation Therapy
Advanced Therapy Dosimeter
Model 35040
 
 
•  Now with Timer Function and wider
dynamic range
•  Ultra long-term stability error of
approximately 0.1% per five years
•  Virtually removes effects of system
leakage during measurement.
Uncorrected leakage < 10 fA over
temperature range
•  Eleven user-defined bias settings
from - 500 to + 500 V
•  Read out in C, A, R, Gy, Sv, Bq,
and more
Introduction
The Model 35040 Advanced Therapy Dosimeter (ATD) is a reference grade instrument
used to measure the charge and current from ion chambers in Radiation Therapy, and provides
bias voltage for all commonly used chambers. The ATD large clear display offers direct
readings of charge, current, time, and radiation units over a wide range. The user can
customize the display for basic use or for specialized applications such as brachytherapy.
The Advanced Therapy Dosimeter exceeds the recommendations of calibration laboratories
for leakage, linearity, and stability by a wide margin. This instrument raises the standard of
Radiation Therapy measurements.
Applications
Radiation Therapy requires great accuracy in the measurement of dose and dose rate values
associated with linear accelerators and radioactive sources. The Model 35040 Advanced
Therapy Dosimeter provides the long-term stability and accuracy demanded for calibrations,
quality assurance programs, and protocols in Radiation Therapy. A unique electrometer
design provides more accuracy than high meg resistor or capacitor feedback electrometers.
The Advanced Therapy Dosimeter is fully stable within five minutes, a fraction of the time
of conventional dosimeters. The flexibility of the instrument optimizes user efficiency and
saves time. In battery operation or using AC Line, the ATD measures dose and effective
exposure time in a single exposure, thus eliminating the need for multiple exposures for
60 Co and brachytherapy measurements. Front panel controls select ion chamber calibration
factors, facilitate entry of temperature and pressure values for air density correction, allow
bias voltage selection, threshold level, timer control, and choice of display screens. The
user-customized display screens can simultaneously show dose, exposure time, dose rate,
effective exposure time, average current/rate, accumulated charge/dose, bias voltage, leakage,
and other important information that ensures the validity of the instrument.
The customization software allows design of 16 screens that display conditions, parameters,
values and text. Up to 32 chamber factors, 11 bias voltages can be programmed. It is PC
compatible and connects via a RS-232 cable.
Features
• Wide measurement range, up to 1.000 µA
and 19.999 mC for HDR Brachytherapy
applications
• Automatic reset and hold of measured
values between exposures
• Front panel adjustment of exposure
threshold and user disable of threshold to
permit manual operation
• Thirty-two ion chamber calibration factors
• Automatic power-down after user-specified
time period, when operating from battery
supply
• Annunciators warn of low battery, low bias,
and operational errors
• Large capacity battery provides eight hours
of continuous operation; fast recharge in
less than three hours, even during operation
• AC line operation over the range 100 to
240 VAC and 47 to 63 Hz without operator
intervention
• Charge and current calibration factors
entered by calibration laboratories at user’s
option
• Front and rear panel ion chamber
connections
• Optional carrying case (Model 37780)
Front Panel Features
Power On/Off key All front panel settings are stored at power-down
and recalled at power-up
Specifications (continued)
Stability Designed for ultra long-term stability error of approximately
0.1% per five years
Leakage Virtually removes effects of total system leakage during
measurement. Uncorrected leakage < 10 fA over temperature range
Linearity Maximum non-linearity variation from straight line of 0.1%
of all charge and current ranges
Resolution 0.005% of range (4.5 digits) for charge, dose, average rate
and average current; 0.05% of range (3.5 digits) for current and rate
Warm-up Fully meets specifications within five minutes of applying
power
Measurement accuracy 64º to 82ºF (18° to 28°C)
Charge ± (0.20% reading plus two counts)
Current ± (0.20% reading plus two counts)
Bias Eleven user-programmable steps from - 500 to + 500 V in
0.1 volt increments
Accuracy ± 0.3 V for loads < 0.2 mA
Front panel selectable
Ion chamber calibration factors Thirty-two user-programmable
calibration factors
Front panel selectable
Display units All practical radiation and electrical units
RS-232 computer configuration For customizing and data transfer
Power requirements Internal Lead Acid Battery
Integral Charger operates 100 to 240 VAC (47 to 63 Hz)
Connectors Triax BNC front/rear 35040
Triax TNC front/rear 35040TNC
Dimensions 9.4 (w) x 10 (d) x 4 in (h) (21.6 x 26 x 8.9 cm)
Weight 10 lb (4.6 kg)
Optional accessories
Carrying Case (Model 37780)
Extension Cable, 20 ft, Triax BNC to BNC (Model 86120)
Adapter, Triax BNC plug to TNC jack (Model 500-111)
Available model(s)
35040 Advanced Therapy Dosimeter
Test Function key Sequence of screens to display firmware revision,
last calibration date, leakage and current, bias voltage and battery
voltage level, and charge and current calibration factors, and times
settings
Detector Select key User selection of one of 32 user-programmed ion
chamber calibration factors with descriptive text, units, and calibration
factors
Air Density key User entry of ambient temperature and pressure;
displays calculated air density corrections; symbol appears on screen
when air density correction is active
Units Select key User selection of rate measurement time base
(s, min, and hr)
Bias Select key User selection of one of 11 user-programmed ion
chamber bias voltage settings from - 500 to + 500 V; displays measured
output bias voltage
Reset/Measure key Displays measurement screen; resets displayed
charge and dose measurement values to zero, re-initializes the
measurement system, and starts/stops the time dose measurement. Up
and down arrows select one of 16 user-designed measurement screens
4-line by 20-character vacuum fluorescent display Provides excellent
visibility in all lighting conditions
Specifications
Dose and rate display
Charge
full scale
Charge
sensitivity
Current*
full scale
Current*
sensitivity
200.00 pC
0.01 pC
200.0 pA
0.1 pA
2.0000 nC
0.0001 nC
2.000 nA
0.001 nA
20.000 nC
0.001 nC
20.00 nA
0.01 nA
200.00 nC
0.01 nC
200.0 nA
0.1 nA
2.0000 µC
0.0001 µC
1.000 µA
0.001 µA
20.000 µC 0.001 µC
200.00 µC 0.01 µC
2.0000 mC 0.0001 mC
20.000 mC 0.001 mC
*Average current is displayed with ten times greater resolution.
Tested. Meets applicable standards.
Effective exposure time ranges
Full scale range
Display resolution
59.99 s
0.01 s
5 hr 33 min 19.9 s
0.1 s