Water calorimeter

Any dosimeter used to determine absorbed dose in an irradiated product has to be calibrated. The adiabatic character of electron beam deposition is used in calorimetry, which is the primary absolute method of measuring the absorbed dose (energy per unit mass). An example of the instrument for this purpose is the water calorimeter developed in Ris0 National Laboratory in Denmark. " This calorimeter is reported to be suitable for electrons from a linear accelerator with energies higher than 5 MeV and... 

The calibration is done by national or secondary standards laboratories. Calibration at the National Institute of Standards and Technology (NIST) involves exposure to either gamma ray source ( Co) over the dose range 10° to 10 Gy, or high-energy electron beam (1 to 28 MeV) combined with a graphite or water calorimeter. ... 

For calibrating the accelerator, poly(vinyl chloride) films and a simple water calorimeter are used in addition to monitoring and controlling the electrical parameters of the accelerator which affect the dose output and, in turn, the absorbed dose. The poly(vinyl chloride) is used primarily for establishing the depth dose in samples irradiated with the scanned electron beam. This film is relatively thin when compared with the range of 10... 

The water calorimeter is used as a production monitor. It consists of a water-filled plastic Petri dish, containing a temperature-sensing device... 

The specific heat of a metal can be found with a water calorimeter. This can be... 

Brede HJ, Hecker O, Hollnagel R. (2000) An absorbed dose to water calorimeter for collimated radiation fields. Nuclear Instruments and Methods in Physics Research AA55 3y. 721-732. 

Burns, D.T. and Morris, W.T., Recent developments in graphite and water calorimeters for electron beam dosimetry at NPL, Proc. Int. workshop on Water Calorimetry, Report NRC-29637, National Research Council of Canada, Ottawa, Canada (1988) 25-30. 

Rudge,t in a recent determination with the water calorimeter, found for carbon dioxide at about 500 atmospheres pressure the extraordinarily high value = 0-45. 

Air is compressed to 22 atm. in a vessel which is kept in a water calorimeter. The work done during compression can be calculated from the initial and final pressures and volumes. The work done is completely converted into heat which is communicated to the calorimeter. The mean of several determinations by this method gave for one great calorie J = 436-1 kgm. The same experiment carried out in the reverse direction is an example of the conversion of heat into work. When the compressed gas is allowed to expand, heat is abstracted from the calorimeter and its temperature is lowered. Three experiments of this sort gave for J the values 449-8, 446-5, and 416-8 kgm. 

The whole apparatus is contained in a water calorimeter, in which the rise in temperature produced by the combustion is measured. In calculating the heat of combustion, we must correct for the heat evolved in the combustion of the iron wire. The calorimeter may be calibrated with a substance of which we know the heat of combustion, or by reproducing with a known electric current the rise in temperature produced by the combustion. The heat of combustion is then equal to the electrical energy produced inside the cylinder. 

Because the heat to be measured is usually brought to a vessel containing water, most calorimeters used in this method can be called water calorimeters . Examples James Watt (1786), Regnault (1840), Favre and Silbermann (1845), Berthelot (1875). Other liquids can be used Favre and Silbermann s mercury calorimeter. 

A common design of semi-adiabatic calorimeters contains thin or thick disc-shape absorbers used mainly in monodirectional beams both for low-energy (McDonald et al. 1972) and for higher-energy electron beams (Bewley 1969). Water calorimeters of the same shape were designed by Brynjolfsson et al. (1963) and Fielden and Holm (1970). 

Crawford was the first to determine specific heats of gases, in 1779 using bladders as containers and in 1788 two thin sheet brass cylinders, one vacuous and the other filled with the gas, which were heated in boiling water and then immersed in two identical water calorimeters. The specific heats at constant volume found in this way were much too high but his determination of the... 

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