Electricity: measuring and testing – Particle precession resonance – Using an electron resonance spectrometer system
Reexamination Certificate
2002-07-17
2004-09-14
Fulton, Christopher W. (Department: 2859)
Electricity: measuring and testing
Particle precession resonance
Using an electron resonance spectrometer system
Reexamination Certificate
active
06791324
ABSTRACT:
FIELD OF THE INVENTION
The present invention, generally, relates to the field of electron spin resonance (ESR) dosimetry.
More specifically, the invention relates to a probehead for an electron spin resonance dosimeter reader, comprising a resonator and an insert extending into the resonator having a guide channel for bringing a sample into the resonator, the sample comprising a dosimeter substance.
Still more specifically, the invention relates to a probehead for an electron spin resonance dosimeter, comprising a resonator, an insert extending into the resonator having a guide channel for bringing a sample into the resonator, the sample comprising a dosimeter substance, and a pressurized air unit for blowing the sample out of the resonator after completion of a measurement.
Moreover, the invention is related to a sample substance for an electron spin resonance dosimeter, comprising a chromium-doped magnesium oxide (Cr:MgO).
BACKGROUND OF THE INVENTION
A probehead of the type of interest in the present context is disclosed in document JP 01 138 484 A.
In the industrial practice, it becomes more and more customary to irradiate products of any kind. For example, various products are irradiated for disinfection purposes or for increasing their durability, respectively. A typical example is the field of hygiene articles, for example baby's diapers. During production, such diapers are packed in batches and are then irradiated batch by batch in order to put them at the customer's disposal in a germ-free condition. It is common practice to convey the articles to be irradiated batch by batch past a source of irradiation, wherein several passes may be provided in order to achieve a predetermined dose of irradiation.
Further, it is a well-established practice to irradiate products and articles in order to exterminate unwanted organisms. In practice this happens for example in connection with food-stuffs, for example spices which are sometimes affected by pathogenic germs and, prior to being processed and distributed, must be treated accordingly.
Still another field of application is the prophylactic irradiation of articles of many kinds in connection with the use of biologic warfare agents if, for example, pieces of mail must be treated as a precautionary measure, because it must be expected that certain pieces of mail containing pathogenic germs are mailed in connection with terrorist attacks.
In all these and many other applications of irradiation, it is, however, desired to properly measure the amount of irradiation and, as the case may be, to document same. This holds true basically independent of the kind of irradiation (gamma rays, electron rays, etc.).
For that purpose, corresponding measuring instruments, dosimeter substances, packaging methods for dosimeter substances and pertinent standards have been developed under the general term “dosimetry”. In the U.S., for example, the American Society for Testing and Materials has developed and published a standard E 1607-96 “Standard Practice for Use of the Alanine-EPR Dosimetry System”. Dosimetry methods are today certified by various official and other institutions. For that purpose, it is necessary to be able to follow-back measuring samples, i.e. to provide a complete documentation.
Conventional dosimeters, as are used, for example, for protecting people in installations where work is done with rays of various kinds, essentially consist of a section of a normal commercial photographic film which becomes blackened under the action of an irradiation. The film sections are developed after a certain period of time has lapsed, and are then evaluated optically, wherein the amount of blackening of the film is a measure for the irradiation dose received. Such film dosimeters are still today used on a broad scale in connection with the measurement of irradiation doses in industrial irradiation processes.
Film dosimeters, however, have the disadvantage that they are relatively complicated in their handling and evaluation. Further, one has found out that they are not stable over an extended period of time. A fast and reliable measurement of irradiation values is, therefore, as much impossible as a long term storage and documentation of the original dosimeters. Finally, the behavior of a photographic film in the present context does not correspond to the behavior of organic tissue being subjected to an irradiation.
Therefore, conventional film dosimeters have increasingly been replaced by so-called alanine dosimeters. In this type of dosimeter, the dosimeter substance consists of alanine, i.e. an amino acid, the behavior of which, for example with respect to gamma rays, corresponds to that of organic tissue to a far more extent as is the case for conventional film dosimeters. In the art, alanine dosimeters are, therefore, referred to by the term “tissue equivalent”. Alanine, moreover, is very stable over an extended period of time, so that irradiated alanine may be again measured after a long period of time has lapsed, without any information having gone lost. Typically, doses of irradiation of interest in the present context are within the range of between 400 Gy (Gray) and 100 kGy (Kilogray).
As already mentioned above in connection with a standard established in the U.S., alanine dosimeters are conventionally measured and evaluated by utilizing the technique of electron paramagnetic resonance (EPR), also referred to as electron spin resonance (ESR). This is because when alanine is irradiated, so-called “free radicals” are generated, which, in the course of an ESR measurement, show a characteristic spectrum in which the amplitude of the primary line within the spectrum is representative for the dose of irradiation.
Document DE 196 37 471 C2 discloses a dosimeter substance, an alanine dosimeter as well as a method for their production. In this context it is disclosed that alanine dosimeters may be configured for utilizing pill- or film-shaped alanine elements of various geometry.
Document DE 39 03 113 C2 discloses a dosimeter as used for persons working in an irradiation-protected area. Likewise, alanine pills are used as dosimeter substance. The dosimeter itself consists of a small frame-shaped assembly having a corresponding chamber for receiving the alanine pills.
Document JP 02 173 589 A discloses still another dosimeter which is adapted to be evaluated by means of ESR. The dosimeter substance in that case has the shape of a strip and is applied to a small frame-shaped assembly.
Document JP 01 138 484 A mentioned at the outset, discloses a probe feed apparatus for ESR dosimeters. In this prior art apparatus, rod-shaped dosimeter elements are inserted into corresponding, axially extending recesses within a rotating disc, the rotation of which is controlled by means of optical sensors. The rotating disc is located above an ESR sample chamber. By rotating the disc accordingly, various dosimeter elements may be positioned above the ESR sample chamber one after the other and may then be lowered thereinto, where they are held in a reference position by means of appropriate holding elements.
Pressurized air may be fed to the sample chamber from its lower side in order to be able to blow the dosimeter element out of the sample chamber after completion of the ESR measurement.
During an ESR measurement, the ESR signal is measured as an electric mistuning of a resonator housing the sample under investigation. During the resonance transition, the sample absorbs energy and, hence, the resonator, having been tuned before, becomes mistuned. For that purpose, the external magnetic field acting on the resonator is conventionally swept slowly so that depending on the sample material and the complexity of the ESR spectrum, one or more resonance lines are generated.
Classical ESR spectrometry is limited in this context to the analysis of the particular appearance of the spectrum, i.e. the number, position and shape of the spectral lines which are recorded and analyzed. Although signal intensity plays a certain roll in that regard, conventional ESR
Jiang Jin Jie
Kamlowski Andreas
Maier Diether
Schmalbein Dieter
Schmidt Thomas
Bruker Biospin GmbH
Fulton Christopher W.
Vargas Dixomara
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