Radiological museum

These "relics" are almost never exposed to the public and generally remain stored in some corner of the hospital, or at most exposed on the shelf in an office where only a few people pass, who perhaps in some cases also do not know exactly how or when they were used.

Wire electrometer and condenser ionization chabers for dosimetry in radiotherapy beams

This equipment manufactured by the American company Victoreen and distributed in Spain by the Giralt Laporta house was used to measure the radiation dose in beams of radiotherapy photons (or more precisely to measure the magnitude of exposure, in roentgens, a somewhat outdated unit today). . Along with the manual in English there is a typewritten Spanish translation dated 1967, although the calibration certificate and the measurements of a cobalt unit that were kept in the same box were from the eighties.

The set is made up of three condenser-type ionization chambers to measure in different energy ranges (from superficial radiotherapy X-rays to energies of the order of 1 MeV) and an electrometer in which the chambers were inserted both to charge them before the measured as for later reading. The operation is simple: in each detector there is a cylindrical condenser that is charged before irradiation, and at one end of the condenser there is an air chamber that, when ionized by the effect of radiation, partially discharges the condenser in proportion to the dose received. ; When the detector is connected to the electrometer after being irradiated, the degree of charge is translated by a purely electrostatic force into a greater or lesser deflection of a conducting wire whose shadow is projected on a small graduated scale, which, magnified by an optical system, can be Observe through the eyepiece of the electrometer.

Pen Type Direct Reading Personal Dosimeter

We do not know exactly when the one in the photograph was used, although we assume it could have been in the 1970s or early 1980s. These dosimeters were designed to be carried in a coat pocket and measure the worker's cumulative exposure over time. over a certain time. The operating principle is similar to that of the ionization chambers that we showed above: a capacitor whose charge reduces as the dosimeter is irradiated, although in this case the reading is seen through an eyepiece located at one end of the dosimeter itself. dosimeter. The charger shown in the photograph was used to recharge the capacitor and set the scale to zero.

These dosimeters were not very reliable for recording exposure over long periods because the capacitor tends to discharge slowly, producing a progressive increase in reading even without radiation. Likewise, a mechanical shock can change the indication of the dosimeter.

Although they are still marketed in some countries, when an individual direct-reading dosimeter is needed, more modern and reliable devices with digital reading are recommended, while for routine personal dosimetry of workers, passive dosimeters are used, which are read monthly in authorized laboratories. officially.

Monitor de radiación “Babyline 31”

The Babyline, from the French company Nardeux, was for a long time the most widely used radiation monitor for area dosimetry in Spain and probably throughout Europe. Although it is somewhat more modern than the two previous detectors (ours is from 1977), in most facilities it has already been replaced by more current equipment or is used only for educational purposes, as is the case in our hospital.

It is also an ionization chamber, together with the necessary electronics to measure not only the accumulated dose but also the dose rate in real time, its main application being the monitoring of radiation levels in workplaces. This model included a small radioactive strontium-yttrium check source that can be stored in a housing located on the equipment itself (being a beta source, the housing plate is enough to absorb the radiation, but if you find one of these, better not to play with the plate where it says "source controle")

The detailed information found in the manual is striking (although all in French), which includes construction characteristics, electronic diagrams and even a graphic record of the oscillations of the background signal on the most sensitive scale with the handwritten legend.

Although refurbished versions of the Babyline continue to be sold, more modern equipment with digital readout and automatic range selection is generally preferred today. In addition, the hood that covers the chamber is designed to estimate the dose that would be absorbed in tissue at a depth of 3 mm, but the currently most recommended magnitude for this type of detector is another: the environmental dose equivalent H*(10) (which regardless of subtleties and technicalities comes to be approximately the dose at 10 mm depth).

We understand that this detector was designed in Spain, specifically at the former Junta de Energía Nuclear (predecessor of the CIEMAT).

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