EP1789818A1

EP1789818A1 - Detecting device based on a synthetic diamond

Info

Publication number: EP1789818A1
Application number: EP05792199A
Authority: EP
Inventors: Marie-Joséphine GUERRERO; Philippe Bergonzo; Dominique Tromson
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2004-09-03
Filing date: 2005-09-01
Publication date: 2007-05-30
Also published as: CA2577186A1; FR2875014A1; FR2875014B1; WO2006024661A1; JP2008511826A; US20080061235A1

Abstract

The invention relates to a detector comprising a sensing plate (2) formed of a thin synthetic diamond plate. The invention is characterized in that it comprises means (11, 4) for heating the sensing plate, said heating means comprising a thin heating plate (4) whose material is essentially constituted of carbon atoms. The invention also relates to a device comprising a detector of the aforementioned type, to a measuring method that uses said detector, and to a method for producing this detector.

Description

DETECTION BASED ON SYNTHETIC DIAMOND

GENERAL TECHNICAL FIELD

The present invention relates to detection based on synthetic diamond. More precisely, it relates to detectors of radiation and particles, in particular of type X, gamma, electrons, protons.

The detectors according to the invention can be used for the metrology and the control of radiation sources, such as particle accelerators used in the medical field (radiotherapy, radiology, etc.) and / or synchrotron-type radiation sources for applications such as measurement of radiation doses, radiation dose rate, detection of the position, intensity and profile of a beam.

The invention also relates to the manufacture of such detectors.

Natural diamond has many interests in the production of radiation detectors that meet specific conditions of use, such as the detection of radiation in a hostile environment or the X-ray metrology. It is indeed a radiation-resistant material, acid solutions and high temperatures (<600 ° C).

For online measurement or metrology of radiation, various criteria are also required in relation to the intended application, such as the possibility of manufacturing very thin layers and / or low atomic number, or to avoid the use of non-equivalent tissue material in the vicinity of the detector - an equivalent tissue material is a material in which the deposited radiation dose is close to that deposited in the human body.

Metrology (radiation dose, beam profile) on medical accelerators is expanding, and radiation dose and sub-beam dose rate need to be measured with tissue equivalent material. The potentialities of diamond evaluated in this area show the possibility of producing miniature dosimeters that can allow for example the measurement of the mapping, as well as the point measurement of dose.

Similarly, in the metrology of X-ray beams and synchrotron light sources in particular, it is necessary to be able to insert, permanently in the light line, a thin non-perturbative device for measuring intensity, position and profile of the light. light bleam.

The use of natural diamond crystals as detectors is known, particularly for medical radiotherapy. These devices have many advantages.

Diamond has a high mechanical strength and is also resistant to corrosive environments and very high doses of radiation.

Diamond, composed of carbon atoms, is a material that is not harmful to the human body, and may have biocompatibility and resistance to biomedical environments.

The low atomic number Z of diamond (Z = 6) allows its use for irradiating beam measurement without significant or total absorption.

Diamond can therefore be used in 'online' metrology. A low Z material will subsequently be defined when its atomic number is less than or equal to 8.

The atomic number of the diamond is close to the equivalent atomic number of the human tissues (7.42 for the muscles, 5.94 for the fat, ie about 7 on average) and the dose in radiotherapy measured by a diamond detector can to be easily related to that received by a patient: the diamond is a tissue equivalent material.

The detectors of the prior art are small which is an advantage for new treatments in radiotherapy (IMRT).

Previous detectors however have disadvantages. Their manufacture is unitary, that is to say that each natural diamond sample must be pre-selected in order to obtain gems having the characteristics appropriate to medical dosimetry measurements. Each gem allows the realization of a single detector, the reduced size natural samples that do not allow to manufacture several devices whose characteristics would be identical. Each detector must be calibrated and calibrated individually.

It follows from the foregoing a prohibitive cost of the detectors. In addition, it is not easy to guarantee the supply of natural diamonds whose properties meet the specifications.

Finally, the performances of the natural diamond devices are often guaranteed only if pretreatment of the detectors (for example by daily pre-irradiation). This step imposes an additional cost due to the duration of irradiation, as well as the unavailability of the equipment during the pretreatment period.

In order to overcome these drawbacks, it is proposed in the prior art to use synthetic diamonds for the manufacture of detectors.

It is indeed possible to manufacture synthetic diamond. The technique of chemical vapor deposition (CVD) or "Chemical Vapor Deposition" according to the Anglo-Saxon terminology generally used by those skilled in the art is the most likely to allow the manufacture of a material having the desired performance. for the detection of radiation. The synthesis makes it possible to reduce the cost of the detectors, because of high manufacturing yields.

It is indeed possible to manufacture on a large surface and in series. Typically, samples can be synthesized over several centimeters in diameter. Detectors can also be manufactured according to the demand, which allows an optimization of the electrical performances with respect to the desired application.

Finally, it is possible to make a mosaic of detectors of identical characteristics for imaging, and / or to integrate the devices with other equipment.

Unfortunately, the current techniques for making synthetic diamond only readily allow the manufacture of a low cost polycrystalline material. However, the characterizations of synthetic diamonds made by CVD on a substrate other than diamond have shown that the last limitations to the improvement of the detectors are related to the diamond manufacturing process and come from the polycrystalline nature of the material. Electrical defects are identified and may be due to the inhomogeneous structure of the material (grains and grain boundaries), but also to the presence of low concentrations of impurities.

These characteristics of the synthetic diamond involve trapping and desiccating phenomena of the charge carriers during the use of the detector. These phenomena are responsible for the evolution over time of the sensitivity of the detectors.

Characterization techniques commonly used for the study of defect concentrations in synthetic diamond have made it possible to classify electrical defects according to several categories. Each trap can be defined by a level of energy in the forbidden band of the diamond. The modification of the state of charge of this energy level (by dépiegeage and trapping) as a function of the thermal energy of the detector makes it possible to define it. We thus distinguish:

- the levels of traps whose thermal energy necessary for the dépiegeage is lower than that corresponding to the ambient temperature. The carriers responsible for the electrical signal under irradiation can be captured on these levels at room temperature and are released almost instantaneously by thermal activation. This level of trap can therefore be considered as 'stable' or inactive when using the device at room temperature;

deep trap levels, whose thermal energy required for the dépégage is very high compared to that corresponding to the ambient temperature (temperature> 200 ⁰ C). Under irradiation, these levels will be gradually "filled" until saturation is reached, heat energy at room temperature then being insufficient to induce a phenomenon of dépiegeage. The generated carriers are no longer disturbed and pass freely through the material. This results in a stable behavior of the detector under radiation during its use at room temperature. The contribution of these levels of traps has long been commented in the diamond since their filling contributes to the progressive increase of the sensitivity of the detector. This stage of progressive filling of the levels of deep traps is recognized in the literature under the names "pumping" or "priming"; - the levels of shallow traps, whose thermal energy necessary for the dépiegeage is close to that corresponding to the ambient temperature. These levels are binding for the use of diamond detectors for industrial applications. Indeed, the proximity of the temperature of thermal activation of the levels of traps relative to the ambient temperature contributes to the progressive dépiégrage carriers of these levels with time constants of up to several minutes depending on the detectors. Thus, when stopping the use of a device for a few moments, so its irradiation, a transient phenomenon will be observed during its reuse. This phenomenon is highly restrictive since it requires the user to know the prior art of the use of the device under radiation in order to be able to interpret its detection behavior. The time constants are then of the order of a few seconds to a few hours, so can interfere with the daily use of an industrial device.

As a result, the electrical and sensing performance of synthetic diamond detectors is generally less than that of a naturally selected material drastically. The reproducibility of the measurement may be affected, the response times may be longer and the nonlinear detection characteristics. PRESENTATION OF THE INVENTION

The invention proposes to overcome these disadvantages without affecting the advantages of synthetic diamond.

An object of the invention is to provide a detector that does not exhibit transient destacking of the shallow levels in the synthetic diamond. One of the other objects of the invention is to propose a detector which allows a neutralization of defects of the polycrystalline layer, for a stabilization of the response of the polycrystalline diamond detector.

One of the aims of the invention is to propose a detector comprising synthetic diamond which can be manufactured industrially and thus have a low cost.

Another object of the invention is to provide a detector that can be of large area, or mosaic.

Another object of the invention is to provide a built-in detector of small size.

One of the other objects of the invention is to propose a detector that generates only a very small radiation disturbance.

For this purpose, the invention proposes a detector comprising a detector plate formed of a synthetic diamond thin plate, characterized in that it comprises means for heating the detector plate, said heating means comprising a thin heating plate. compatible with the intended detection application, ie whose material has the same tissue equivalence properties as the detector plate for medical applications, or the same transparency properties (low Z) as the detector plate for beam metrology applications. The thin heating plate is advantageously made of a material essentially based on carbon atoms.

The invention is advantageously completed by the following features, taken alone or in any of their technically possible combination:

the detector plate consists of polycrystalline diamond, doped or not;

the material of the heating plate is a tissue equivalent material for medical applications; the heating plate material has a low atomic number for beam metrology applications;

the heating plate consists either of synthetic diamond, of doped or non-doped polycrystalline type, or of a carbon-bonded material, of the type carbon in the form of amorphous diamond, nanocrystalline diamond or carbon in the form of amorphous polymer, or graphite;

the detector plate and the heating plate are in contact with each other; the heating plate is separated from the detector plate by an electrically insulating intermediate plate and the material of which has an atomic number at least close to the atomic number of the material of the detector plate;

the material of the intermediate plate is a tissue equivalent material for medical applications,

the material of the intermediate plate has a low atomic number for beam metrology applications;

the intermediate plate consists either of synthetic diamond, of polycrystalline doped or non-doped type, or of a carbon-bonded material, of carbon type in the form of amorphous diamond, nanocrystalline diamond or carbon in the form of amorphous polymer, or of graphite;

- The heating plate extends substantially to the right of the entire surface of the sensor plate;

the detector plate and / or the heating plate are doped; the doping element is boron and / or phosphorus and / or nitrogen;

the detector comprises at least one measurement electrode in contact with the detector plate;

it comprises electrodes for the passage of a current in the heating plate; the electrodes are based on either synthetic diamond, of doped or unpoped polycrystalline type, or of a material based on carbon bonds, of the amorphous diamond carbon type, nanocrystalline diamond, carbon in the form of amorphous polymer, graphite, is still based on a metal or a metal alloy. The invention also relates to a measuring device comprising such a detector.

The invention also relates to a measurement method using such a detector and a method of manufacturing such a detector. PRESENTATION OF FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the accompanying drawings, in which: FIGS. 1A to 1D show schematically in longitudinal section a first method of manufacturing a detector according to the invention;

- Figures 2A to 2D schematically show in longitudinal section a second method of manufacturing a detector according to the invention;

FIGS. 3A to 3C show different possible positions of the electrodes on the detector plate;

- Figure 4 shows schematically a heating device of the heating plate; and

- Figures 5A and 5B show schematically different electrode configurations on the surface of the plates. In all the figures, similar elements bear identical reference numerals.

DETAILED DESCRIPTION

In order to overcome the problem of transient de-scaling of shallow levels in a synthetic diamond-based detector, one solution is to use the detector at a temperature to maintain a "stable" state of populations trapped in the material.

Instead of keeping the device at a low temperature in order to block the carriers trapped on the filled levels (a solution that comes naturally to mind), a method according to the invention consists on the contrary in heating the detector to a few tens of degrees (for example). example between 50 ^° C. and

15O ⁰ C). The method according to the invention thus avoids the use of an installation of cryogenic equipment.

Recent studies on the physical parameters of the levels of traps concerned have shown that the method according to the invention could work.

It is therefore necessary to produce a detector with uniform heating by a material that does not disturb the diamond detector layer or the radiation to be detected. To ensure the temperature rise of the detector, however, conventional electric heating can not be suitable, as the advantages of diamond (low Z, fabric equivalence, chemical inertness, etc.) would be nullified if additional material, including physical characteristics are too far from those of diamond, was present in the detector.

Indeed, in medical and detection applications, the detector is interposed on the beam, but must not screen or disrupt it. It is therefore not only the detector layer, but also the entire detector which must not be disturbing with respect to the radiation.

The invention thus proposes a detector comprising a detector plate formed of a synthetic diamond thin plate and means for heating the detector plate. The heating means comprise a thin heating plate whose material is a tissue equivalent material for medical applications, or has a low atomic number for beam metrology applications.

The material of the thin heating plate consists essentially of carbon atoms. In the remainder of the present description, the term "material consisting essentially of carbon atoms" means a material whose chemical composition, regardless of its crystalline or amorphous structure, comprises almost exclusively carbon atoms. If other chemical components are present in the material, then they are residues or dopants. The material then approaches a "diamond" material. There is then a material both thermal conductor and transparent to the radiation to be detected. The absence of "non-diamond" materials in the vicinity of the detector makes it possible not to disturb the measurement of the beam with foreign elements, whether for a dose measurement or otherwise. Thus, the material of the heating plate may be diamond, preferably synthetic, or a carbon-bonded material, such as, for example, amorphous diamond-shaped carbon or "Diamond Like Carbon" (DLC), nanocrystalline diamond, carbon in the form of amorphous polymer or "Polymer Like Carbon", etc.

In all cases, the material of the heating plate used is of low resistivity, and the injection of an electric current allows its heating by Joule effect.

Advantageously, the heating plate comprises a thin layer of diamond doped with boron or phosphorus or nitrogen, for example. Such doping makes it possible to give the heating plate a reduced resistivity with respect to the intrinsic material. It then becomes possible to circulate an electric current in the heating plate thus allowing its temperature rise.

It is understood that the heating plate may be any layer of diamond or carbon-bonded material whose resistivity would have been reduced after a particular treatment. A first possible method of manufacture is to integrate in the detector having a first diamond detection plate a second plate whose role is to allow the heating of the detector. The coupling of this heating plate of low resistivity to the detector diamond is ideally made by stacking two layers of different resistivity during their synthesis. For example, a doped layer of a few tens of microns may be directly deposited on the intrinsic diamond layer used for the detection of incident particles or photons.

A second possible method of manufacture consists of using two distinct layers, one of low resistivity for heating and the other of high resistivity for detection, and putting them in contact mechanically.

It may be interesting to intercalate between the two layers an intermediate layer whose role would be to electrically isolate the detector - in which very small currents must remain measurable - the heating part - where high current densities can be required. The intermediate layer is also made of a tissue equivalent material for medical applications, or has a number atomic weak for beam metrology applications, to be non-perturbative.

The manufacture of possible embodiments of the detector is detailed in the following developments. FIRST MODE OF REALIZATION AND MANUFACTURE

Fig. 1A shows that in a first step, the synthetic diamond material 2 is grown on a substrate 1 for the detection of radiation.

The diamond is synthesized by chemical vapor deposition (CVD), possibly assisted by a plasma ("Plasma Enhanced CVD" (PECVD)), for example of the microwaves type.

The technique for synthesizing the diamond layer 2 is known to those skilled in the art and makes it possible to obtain a polycrystalline diamond sample 2 if the synthesis takes place on a substrate 1 different from diamond (heteroepitaxy) and a single crystal sample 2 in the case of homoepitaxy.

The following developments apply to a heteroepitaxy on silicon substrate 1, the principle being the same for homoepitaxy, with however a restriction for the size of the growth substrate 1 and therefore that of the final detector.

The deposition conditions for obtaining a diamond detection material are referenced in the literature. They are specific to each reactor and optimized to obtain an electronic quality material.

In the case of a conventional PECVD reactor, these conditions typically vary between 1.5kW and 5kW microwave power, 70 torr at 125 torr pressure in the deposition chamber, 750 to 950 ° C for the deposition temperature . Microwave plasma is obtained by dissociation of a gaseous mixture of hydrogen and methane with possible addition of oxygen.

The thickness of the layer 2 forming the detection plate obtained varies between 20 and 500 microns depending on the intended applications (detection of alpha particles, X-radiation, etc.) on 1 to 2-inch whole substrates or pre-cut samples.

After the synthesis of the plate 2, the sample can be taken out of the first growth reactor to be transferred into a reactor allowing the doping of the material of the plate 2. Preferably, the plate 2 is doped with boron or phosphorus or nitrogen for example.

The doping step of the detector plate 2 is optional.

The synthesis of an intermediate plate 3 in the form of a thin layer superimposed on the plate 2 takes place in a second step, in the doping reactor and without intentional incorporation of impurities. The thickness of layer 3 is typically a few microns. The material of the intermediate plate 3 obtained is intrinsic with residual impurities of dopants.

In a third step, the synthesis of the heating plate 4 in the form of a thin layer takes place by CVD with voluntary incorporation of impurities by resumption of growth on the intermediate layer 3. The thickness of layer 4 is typically about 10 microns. The impurities may be, for example boron atoms in variable concentration, from October ¹⁵ to October ²¹ at / cm ³ for example. This doping technique listed in the literature makes it possible to obtain layers of variable resistivities according to the incorporated dopant concentration. The material of the plate 4 is preferably doped, but may also be undoped.

The stack of materials obtained after the three successive steps is shown in Figure 1 A.

The plate 3 serves as an insulator between the sensor plate 2 and the heating plate 4. The resistivity of the plate 3 is greater than that of the plate

4. The presence of an intermediate plate 3 is optional. It is possible to deposit the heating plate 4 directly in the form of a layer on the detector plate 2.

In a fourth step shown in FIG. 1B, the silicon substrate 1 having served as growth support in the first step is removed. The substrate 1 can be removed by chemical etching using a HF mixture: HNO ₃ . The chemical composition of the mixture makes it possible to selectively etch the growth substrate 1 leaving the layers 2, 3 and 4 obtained in the first three steps described above intact.

FIG. 1C shows that electrodes 10 and 20 allowing the polarization of the plate 2 and the measurement of a signal can be deposited during a fifth step by evaporation on the material of the plate 2.

FIG. 1D shows that contacts 30 and 40 are also made during a sixth step on an upper face of the doped plate 4. The contacts 30 and 40 serve to supply the heating. The geometry, the thickness of the contacts 10, 20, 30 and 40, as well as the material used for the contacts 10, 20, 30 and 40 are adapted according to the intended applications.

For example, for medical applications, the contacts 10, 20, 30 and 40 will be carbon, carbon-bonded material or tissue equivalent material, so as not to lose the advantages of diamond detector plate 2. The electrodes 10 , 20, 30 and 40 are for example based on synthetic diamond, doped polycrystalline type or not, or a material based on carbon bonds, such as carbon in the form of amorphous diamond or "Diamond Like Carbon" (DLC ), nanocrystalline diamond, carbon in the form of amorphous polymer or "Polymer Like Carbon", or graphite.

For non-medical applications, for example beam control, one can also consider evaporating metals or metal alloys whose contact with the diamond plate 4 and plate 2 is ohmic, adapting the thickness evaporated as needed. The metals that can be used are, for example, gold or a Ti / Pt / Au alloy. For example, a gold evaporation of 20 nm to obtain a semi-transparent layer.

The deposits of the contacts 10, 20, 30 and 40 are made according to the required precision, through metal masks or by lithography. All contact evaporation techniques are part of general knowledge, and techniques and materials have been widely listed in the literature. The filing of the contacts 10, 20, 30 and 40 can be achieved by Joule effect evaporation or electron gun, or any other technique known to those skilled in the art. FIGS. 1C and 1D show a possible configuration of the contacts 10, 20, 30 and 40, other polarization and heating configurations are described in more detail below.

SECOND EMBODIMENT AND MANUFACTURE

Fig. 2A shows that in a first step, the synthetic diamond material 2 is grown on a substrate 1 for the detection of radiation. This step is completely identical to the first step described above.

In a second optional step, it is possible to carry out the growth of an intermediate layer 3 on the plate 2. This layer 3 has the same role as that described in the previous second step, and can be obtained under the same conditions. Layer 3 can also be obtained in the intrinsic growth reactor. At the end of the synthesis of layers 2 and 3, the sample is taken out of the growth reactor in order to assemble the device.

In a third step shown in FIG. 2B, the heating plate 4 is assembled. The plate 4 allowing the temperature rise of the plate 2 may be more generally a diamond material having undergone a treatment to reduce its resistivity, a material with carbon bonds, (diamond obtained by other growth techniques, DLC, diamond nanocrystalline, polymer like carbon, etc.) or a material of low resistivity and tissue equivalent for medical applications, or low Z for radiation beam metrology applications. .

The plate 4 can be mechanically assembled on the layers 2 and 3 above. It can be a simple contact, a bonding, a molecular adhesion, etc. The achievement of a mechanical coupling between the detector and heating plates 2 - possibly via the intermediate plate 3 - has the advantage of allowing the combination of materials whose direct growth of a layer on the other is not possible. The range of choices for the materials of the various plates 2, 3 and 4 is then much wider and can thus be adapted to the intended applications. In return, a mechanical assembly may have a heating homogeneity lower than that of a detector made by direct growth of layers. The deposition of the contacts 10, 20, 30 and 40 shown in FIG. 2D is identical to that performed in the first embodiment and described in FIGS. 1C and 1D.

OPERATION

There are two geometrically distinct parts in the operation of the detector. On the one hand, the detection of radiation by the optimized intrinsic diamond layer 2, and on the other hand the temperature rise thereof by the heating plate 4.

Radiation detection is based on the principle of an ionization chamber. FIG. 3A shows that the ionizing radiation 5 interacts with the diamond material of the plate 2 and creates free carriers of the electron-type 6 and holes 7 which, under the action of an electric field 8 applied to the sample, are collected at the electrodes 10 and 20 giving rise to a measurable electrical signal.

Diamond allows this mode of operation because of the width of its bandgap at room temperature (5.5 eV).

FIG. 3A shows that the electrodes 10 and 20 can be evaporated on each face of the diamond plate 2.

FIGS. 1C, 1D, 2D and 3C show that the electrodes 10 and 20 may be on the same face of the diamond plate 2. FIG. 5A shows that the electrodes 10 and 20 may be in coplanar contact configuration on the same face of the diamond plate 2, and FIG. 5B shows that the electrodes 10 and 20 may be interdigitated on the same face of the plate 2 diamond. According to a variant, it is used that the intermediate layer 3 can serve as a rear contact. FIG. 3B thus shows that a conductive deposit 10 is evaporated on the layer 3 to allow the application of a voltage to the plate 2 by means 9, forming for example a voltage source. The signal created by the radiation is then recorded thanks to the electrode 20 on the front face of the plate 2.

Two operating modes can be used: the count mode and the current mode. These two modes of operation are known in instrumentation. Figure 4 shows a device for heating the plate 2 with the thin plate 4 of low resistivity.

Means 11, for example forming a current source, make it possible to produce a current (from 1 mA to 10 mA) and to pass it through the layer 4, between the electrodes 30 and 40 at the surface of the layer 4. The passage of current increases the temperature of the layer 4. The heating due to the circulation of the electric carriers is sensitive and can be easily controlled by the regulation of the current density.

The operating temperature of the detector plate 2 is between 50 ^° C. and 150 ^° C. A calibration as a function of the doping level of the layer 4, the thickness and the geometry of the detector makes it possible to know the current values. necessary to the desired elevation of the temperature.

Likewise, the calibration can also make it possible to measure the residual voltage by means 12 forming a voltmeter and connected between the electrodes 30 and 40 during the current measurement, in order to know the instantaneous resistivity of the heating plate 4, and so allow to know its temperature.

In order to prevent the heating current from disturbing the signal of the detector, the intermediate layer 3 of diamond described in the preceding devices is used. The intermediate layer 3 separates the heating current and the detection current.

The electrodes 30 and 40 may be on the same face of the heating plate 4. As for the electrodes 10 and 20, the electrodes 30 and 40 may be in the configuration of coplanar or interdigitated contacts on the same face of the heating plate 4.

The operation of the detector in the radiation detection mode requires prior calibrations. Before use, the detector plate 2 is characterized under radiation. The response of the detector is analyzed according to the measurement temperature as well as the irradiation history. It is thus possible to study the behavior of the detection device according to the population of the trap levels. The optimum operating temperature of the detector, namely that in which the measurement temperature does not influence the stability, is thus determined.

The heating plate 4 is also characterized before use of the device, by controlling the current level in the heating material, in order to obtain the set temperature defined according to the previous characterizations.

After each use, a reset of the detector can be achieved simply by brief heating of the detector at high temperature (greater than 200 ⁰ C and up to typically 400 ⁰ C). Then, before the first use, a preliminary irradiation of the detector is carried out so as to always be in the same state of filling of the levels of traps. The radiation dose required for the balance of the detector is determined by prior characterization.

To the ready-to-use device, it is possible to attach a calibration sheet and instructions for use comprising: the dose necessary for pre-irradiation;

- the optimal operating temperature also called "set temperature";

the level of current to be applied in the heating layer 4 to obtain the set temperature; the temperature necessary for resetting the device (emptying trap levels), also called "cleaning temperature"; the level of current to be applied in the heating layer 4 in order to obtain the cleaning temperature.

The invention is advantageously used for radiation detection for radiotherapy and beam dose measurement, in X-beam monitors and positioners. In radiotherapy in particular, the device allows the measurement of dose and dose rate of the beam before irradiation of the patient, at a heating temperature that is not dangerous for the patient. The device being designed entirely in material at least close to a tissue equivalent, correction factors usually employed are not necessary, thus simplification and accuracy of the measurement are increased. The device may include means for forming a four quadrant detector.

Claims

1. Detector comprising a plate (2) detector formed of a synthetic diamond thin plate, characterized in that it comprises means (11, 4) for heating the detector plate, said heating means comprising a plate (4). ) thin heating whose material consists essentially of carbon atoms.

2. Detector according to claim 1, characterized in that the plate (2) detector consists of polycrystalline diamond, doped or not.

3. Detector according to one of claims 1 to 2, characterized in that the heating plate (4) consists of either synthetic diamond, polycrystalline type doped or not, or a carbon-bonded material, carbon type in the form of amorphous diamond, nanocrystalline diamond, carbon in the form of amorphous polymer, or graphite.

4. Detector according to one of claims 1 to 3, characterized in that the sensor plate (2) and the plate (4) for heating are in contact with each other.

5. Detector according to one of claims 1 to 3, characterized in that the heating plate (4) is separated from the detector plate (2) by an electrically insulating intermediate plate (3) and whose material consists essentially of carbon atoms.

6. Detector according to claim 5, characterized in that the intermediate plate (3) consists of either synthetic diamond, polycrystalline type doped or not, or a carbon-bonded carbon-like material in the form of amorphous diamond, diamond nanocrystalline, carbon in the form of amorphous polymer, or graphite.

7. Detector according to one of claims 1 to 6, characterized in that the heating plate (4) extends substantially to the right of the entire surface of the plate (2) detector.

8. Detector according to one of claims 1 to 7, characterized in that the plate (2) detector and / or the plate (4) of heating are doped.

9. Detector according to claim 8, characterized in that the doping element is boron and / or phosphorus and / or nitrogen.

10. Detector according to one of claims 1 to 9, characterized in that it comprises at least one measuring electrode (10, 20) in contact with the detector plate (2).

11. Detector according to one of claims 1 to 10, characterized in that it comprises electrodes (30, 40) for the passage of a current in the heating plate (4).

12. Detector according to claim 11, characterized in that the electrodes are based on either synthetic diamond, polycrystalline type doped or not, or a material based on carbon bonds, carbon type in the form of amorphous diamond, diamond nanocrystalline, carbon in the form of amorphous polymer, graphite, is still based on a metal or a metal alloy.

13. Detector for radiation beam metrology according to one of Claims 1 to 12, characterized in that the materials of the detector plate (2), the heating plate (4) and the intermediate plate (3) ), are materials of atomic number less than or equal to 8.

Medical dosimetry detector according to one of Claims 1 to 12, characterized in that the materials of the sensor plate (2), the heating plate (4) and the intermediate plate (3) are equivalent materials fabrics.

15. Imaging device, characterized in that it comprises at least one detector according to one of claims 1 to 14.

16. Device according to claim 15, characterized in that it comprises means for forming a four-quadrant detector.

17. Measuring method by a plate (2) detector formed of a synthetic diamond thin plate, characterized in that it comprises the step of heating the detector plate by heating means (11, 4), said heating means comprising a thin heating plate (4) whose material consists essentially of carbon atoms.

18. The method of claim 17, characterized in that it comprises the step of, during a measurement, bring the temperature of the plate (2) detector to an operating temperature of between 50 ^° C and 15O ⁰ vs.

19. The method of claim 17, characterized in that it comprises the step of, between two measurements, bring the temperature of the plate (2) detector to a reset temperature above 200 ° C.

20. A method of manufacturing a detector comprising a plate (2) detecting formed of a synthetic diamond thin plate, characterized in that it comprises a step of coupling a thin plate (4) for heating the plate ( 2) detector at said detector plate (2), the material of the heating plate (4) consisting essentially of carbon atoms.

21. The method of claim 20, characterized in that it comprises a step of performing the coupling by depositing the plate

(4) heating in the form of a thin layer by chemical vapor deposition.

22. The method of claim 20, characterized in that it comprises a step of performing the coupling mechanically of the heating plate (4) to the right of the detector plate (2).

23. Method according to one of claims 20 to 22, characterized in that it comprises a step of performing the coupling through an intermediate plate (3) whose material consists essentially of carbon atoms. .

24. The method of claim 23, characterized in that it comprises a step of depositing the intermediate plate (3) on the plate (2) detector in the form of a thin layer by chemical vapor deposition.

25. Method according to one of claims 20 to 24, characterized in that it comprises a step of depositing electrodes (10, 20, 30, 40) on the sensor plate and the heating plate.