# PHYSICAL AND CHEMICAL PROPERTIES OF A WATER CALORIMETER

> **NIH NIH R01** · YALE UNIVERSITY · 1988 · $162,178

## Abstract

The temperature-regulated, flexible, glass-core calorimeter
containing nitrogen-saturated water at 4 degrees C yields a dose-
to-water from 4 MV x rays that is 1.006 times greater than that
recorded by an ionization chamber.  It remains unresolved as to
whether this result means that both systems yield essentially the
same, accurate dose, or whether a thermal defect in the water
and one or more inaccurate parameters applied to the ionization
measurements may be of the same magnitude and direction.

The dosimetry of neutron and heavy charged-particle beams is
currently established with calibrated, A-150-plastic ionization
chambers or calorimeters made of the same material.  Because of
uncertainties in physical parameters, the calibrations of neutron
beams with ionization chambers have uncertainties of 5.4-10.8%
depending on energy.  Calibrations with A-150 calorimeters suffer
from a 4% thermal defect, and the conversion of dose-to-(A-150)
to dose-to-muscle has an uncertainty of 2.6-9.7% due to the
kerma factor ratio of muscle to A-150.  Because the atomic
composition of tissue-equivalent liquid (TEL) can be readily
adjusted to match that of the tissue of interest, i.e., muscle, a
TEL calorimeter modeled on the present water calorimeter has
the potential for reducing the uncertainty of the dosimetry of
these radiations.

So as to improve the accuracy of radiation-therapy dosimetry, it
is proposed that the following research and development be
undertaken:  1.  Measure the thermal defect of water and a
variety of TEL's using proton beams in the range 1-40 MeV, and
evaluate the effect of dissolved gases and radical scavengers.  2.
Measure the specific heat of promising TEL's relative to water
using precision thermometric and electronic instrumentation.  3.
Study the effect of low operating temperatures on the
performance of the TEL calorimeter where increased viscosity
will reduce convection currents.  4.  Using 4 MV x rays, compare
the dose-to-muscle from the TEL calorimeter with that obtained
from ionization-chamber dosimetry and from the water
calorimeter.  5.  Using 160 MeV protons, and subsequently high-
energy neutrons, compare the dose-to-muscle from the TEL
calorimeter with that obtained from an A-150 ionization chamber.
6. Expand the evaluation of the water calorimeter to include a
wide range of x-ray and electron beams, and compare the results
with the doses obtained with ionization chambers.

## Key facts

- **NIH application ID:** 3176607
- **Project number:** 2R01CA038563-04
- **Recipient organization:** YALE UNIVERSITY
- **SAM.gov UEI:** FL6GV84CKN57
- **Principal Investigator:** ROBERT J SCHULZ
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1988
- **Award amount:** $162,178
- **Award type:** 2
- **Project period:** 1985-01-01 → 1990-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3176607

## Citation

> US National Institutes of Health, RePORTER application 3176607, PHYSICAL AND CHEMICAL PROPERTIES OF A WATER CALORIMETER (2R01CA038563-04). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3176607. Licensed CC0.

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