WO2013186798A2 - Détecteur basé sur fibres optiques de scintillation pour suivi de particules chargées ayant une application dans la réalisation de détecteur de plage résiduelle employant un procédé de compression et de réduction de canaux de lecture - Google Patents

Détecteur basé sur fibres optiques de scintillation pour suivi de particules chargées ayant une application dans la réalisation de détecteur de plage résiduelle employant un procédé de compression et de réduction de canaux de lecture Download PDF

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WO2013186798A2
WO2013186798A2 PCT/IT2013/000168 IT2013000168W WO2013186798A2 WO 2013186798 A2 WO2013186798 A2 WO 2013186798A2 IT 2013000168 W IT2013000168 W IT 2013000168W WO 2013186798 A2 WO2013186798 A2 WO 2013186798A2
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fibers
detector
channels
scintillating
strip
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PCT/IT2013/000168
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WO2013186798A3 (fr
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Domenico LO PRESTI
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Infn Istituto Nationale Di Fisica Nucleare
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Priority to EP13745732.1A priority Critical patent/EP2859382A2/fr
Publication of WO2013186798A2 publication Critical patent/WO2013186798A2/fr
Publication of WO2013186798A3 publication Critical patent/WO2013186798A3/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T5/00—Recording of movements or tracks of particles; Processing or analysis of such tracks
    • G01T5/08—Scintillation chambers

Definitions

  • the present invention relates to segmented detectors with segments in the form of strips, in particular detectors in which the strips are formed by scintillating fibers.
  • the invention allows the realization of position detectors and trackers for charged particles with a reduction in the read-out channels, advantageously also applicable to residual range measurement.
  • the invention also includes a method for compressing the read-out channels which is applicable preferably, but not exclusively, to large- area and high spatial resolution real-time detectors for charged particles.
  • the compression method according to the invention is a method for compressing the number of read-out channels applicable to any linearly segmented position detector.
  • a detector of charged particles is a device which is sensitive to passing of the particle and able to produce a si nal proportional to the energy released by the particle along the path inside the detection volume.
  • a detection system with linear segmentation is a device in which the detection area is uniformly divided up into segments so as to extract, in addition to the information relating to passing of a particle, i.e. a hit or event, also information regarding the crossing position of the particle in the sensitive area.
  • the segment may be in the form of a strip or pixel.
  • one of the coordinates, x or y, of the point of entry of the particle may be extracted.
  • identification of the pixel crossed by the particle identifies simultaneously the two impact coordinates.
  • a schematic illustration of linear segmentation is shown in Figure 1.
  • the point of access to a single segment of the segmented detector is called a "read-out channel".
  • This channel commonly provides an analog signal proportional to the energy released by the particle in the detector volume corresponding to the segment.
  • Extraction of the desired information, energy or arrival time requires processing of the signal and consequent conversion into numerical format for subsequent acquisition and processing.
  • the analog signal which is typically a high-speed current pulse, must be suitably amplified, so as to optimize the signal/noise ratio, and then compared with a threshold by means of a comparator or converted into numerical format by means of an analog digital converter.
  • a comparator or converted into numerical format by means of an analog digital converter.
  • the technique of segmenting the sensitive area of a particle detector in order to detect, in addition to passing of the particle, also the position crossed inside the sensitive area of the detector is used in many scientific and industrial fields with applications ranging from imaging to environmental monitoring and medicine, from large-scale physics experiments to industrial control systems.
  • micro-strip gas detectors to silicon detectors, where the strips consist of strips of Si-based or Ge-based materials, or detectors where the strips are formed by scintillating optical fibers.
  • Table 1 shows a comparison between a number of devices for performing tracking by means of scintillating optical fibers according to the prior art.
  • Linear segmentation detectors are known and are made for example using scintillating optical fibers which are arranged next to each other longitudinally so as to form a strip which forms the entire detection area.
  • the scintillating fibers replace the strips of the detector and the detection surface is formed by arranging N scintillating fibers next to each other.
  • scintillating fibers with a square or circular cross-section (up to 200 urn side size or diameter or more) and length of up to several km.
  • the maximum length is typically 3.2 m with fibers having a square or circular cross-section ranging from 200 um to 5mm as regards side size or diameter [5] .
  • These optical fibers consist of a suitably doped polystyrene core and an optical coating or cladding consisting of polymethylmethacrylate (PMMA).
  • a charged particle which passes through the core releases energy which is absorbed and output again promptly in the form of isotropically emitted scintillating light.
  • the materials of the core or cladding are chosen with refraction indices such as to ensure total reflection of the light generated inside the fiber in a range of angles limited by the critical angle ⁇ , depending on the two refraction indices neore and riciad.
  • a part of the light produced by means of scintillation is channeled inside the fiber and transmitted in the two opposite directions of the said fiber which acts as a light guide.
  • FIG. 2 A diagram illustrating the operating principle of the scintillating optical fiber is shown in Figure 2 [5].
  • Extraction of the desired information, energy or arrival time requires processing of the signal and consequent conversion into logic format for subsequent acquisition and processing.
  • the measurement of the residual energy of a charged particle after crossing a volume is used to produce an image of the same volume.
  • the information relating to the point of crossing of the volume for which an image is to be produced is associated with the residual energy information.
  • the residual energy is conventionally measured in two ways: 1) Calorimetric measurement: the residual energy is
  • the charged particles when crossing a medium, do not release their energy uniformly.
  • the particle loses more energy as its slows down inside the medium.
  • the kinetic energy is proportional to the square of the particle velocity.
  • the release of energy increases exponentially until total stoppage of the particle occurs and during the last section produces what is known as the "Bragg peak", namely during the last few millimeters of its travel path the particle releases suddenly a significant amount of its initial energy.
  • PRIMA - Active area 512 digital ASIC YAG:Ce crystals read event reconstruction, low Proton channels x 4 by pnotodiodes reconstruction rate (1 MHz).
  • the system envisages on proton automated scanning radiography Single particle of the films with with nuclear tracking and
  • Table 2 shows the results of the comparison between different systems according to the prior art.
  • the number of channels increases with the dimensions at a fixed resolution or the reading electronics has few channels, but is complex and/or slow.
  • the tomography images thus recorded in any case must be processed offline.
  • the present invention relates to segmented detectors with segments in the form of strips, in particular detectors in which the strips are formed by scintillating fibers, able to solve the problems posed by the prior art, by means of reduction and compression of the number of read-out channels.
  • the strips are formed by scintillating fibers, preferably a plurality of fibers which are all folded in the same manner and are arranged next to each other so as to form strips of scintillating fibers folded as mentioned above.
  • the strips of scintillating fibers are folded at least once and the ends form relative to each other an angle 0 ⁇ 90 ⁇ so as to be arranged in planes which are aligned and parallel and are in contact with or spaced from each other.
  • the strips of folded scintillating fibers may be used as position detectors and their arrangement allows the formation of a position detector by means of a single folded strip which acts as detector for the two impact coordinates of a particle in the sensitive area of the detector, one for x coordinate and one for the y coordinate, reducing by half the channels required to form an x, y position detector with two separate strips in the quadruple coincidence condition as described below.
  • Another innovative feature of the invention relates to halving of the read-out channels of a tracking detector consisting of two detection surfaces which are parallel to each other, said halving being obtained by means of strips of scintillating fibers which are folded in a U shape so as to form the surfaces of position detectors of a tracker.
  • the invention relates to detectors in which the strips folded as described above are optically coupled with clear fibers or fibers of the WLS (wavelength shifter) type.
  • Another object of the present invention is the realization of segmented strip detectors with a reduced number of read-out channels.
  • the detectors according to the invention are in particular detectors comprising strips of scintillating fibers and may be one-dimensional detectors, two-dimensional detectors or tracking detectors and may also be combined with other types of residual-range detectors which are known per se, for example those made with plastic scintillation sheets arranged next to each other.
  • Another characteristic feature of the invention therefore consists in an apparatus for radiography or tomography using charged particles, for example carbon ions or protons, comprising one or more tracking detectors associated with at least one device for measuring the residual range of the particles, which uses the channel compression and reduction method as described below and the different techniques for realizing the trackers according to the invention.
  • the method for compressing the number of read-out channels of a segmented position detector for charged particles envisages suitable grouping (as described below) of the strips at the two read-out ends thereof, so as to obtain a compression factor equal to a 2 ⁇ in quadruple coincidence.
  • Reduction of the read-out channels of the track detector based on scintillating fibers is obtained, not only by using the method for compressing the channels according to the invention, but also with the aid of strips of scintillating fibers folded in a U shape and arranged so as to create pairs of tracking surfaces instead of single surfaces, for the x direction and y direction.
  • the main applications of the method and the devices according to the invention consist in medical imaging and beam diagnostics, which is an aspect of importance for medical apparatus employed in therapy using charged particles, for example carbon ions or protons, in order to improve the performance of the existing devices and machines.
  • the main advantages in this connection are the possibility of performing extremely rapid and high-resolution charged-particle radiography of large areas at a low cost, while also allowing precise positioning of the patient and beam diagnostics in real time. More generally, advantages, such as the reduction of the read-out channels for a segmented strip detector and consequent improved performance of the acquisition electronics so as to approach real time, assume a key role in different scientific sectors, including the sector of telecommunications, advanced medicine, laser physics and high-energy physics.
  • Figures 1A and IB show the sensitive area of a detector before (Fig. 1A) and after segmentation into segments or strips (Fig. IB) in one direction; in the example shown the strips are 7 in number; in the field of scintillating-fiber detectors, each strip comprises at least one fiber;
  • Fig. 2 is a functional diagram of a scintillating fiber which shows the photogeneration mechanism during passage of a particle P through a scintillating core C;
  • Fig. 3 is a schematic perspective view of the basic element of a tracker, formed by means of a single strip of N scintillating fibers (not shown) suitably folded at an angle a, in this case a ⁇ 0;
  • Fig. 4A shows a detail of the routing diagram of the fibers for application of the compression method. The compressed channels PG and SG lit up during passage of a particle are clearly shown.
  • Fig. 4B shows a detail of the ends 1 and 2 of Fig. 3, grouped together generically here as PG and SG.
  • Fig. 4C shows a graph of the intensity of the signals output from the compressed channels in the conditions of the example.
  • Fig. 6 shows a detector realized by means of the arrangement next to each other in a direction of S basic structures such as the one shown in Fig. 3, where the useful detection area is a rectangular trapezium;
  • Fig. 8 shows two strips folded in a U as in Fig. 7, rotated through 90° relative to ach other, so as to obtain a double tracker; the mutually perpendicular surfaces of the two trackers are arranged next to each other and form square-shaped pixels;
  • Fig. 9 shows the result of using 4 strips of scintillating fibers folded as in Figure 7 so as to obtain a total of 4 trackers; repetition of the procedure using N strips of scintillating fibers folded as shown in Figure 7 results in the formation of N trackers;
  • Fig. 10 shows an arrangement for the tracking of charged particles with 12 detection surfaces xy formed using 12 strips of scintillating fibers folded as shown in Figure 7;
  • Fig. 12 shows an example of a residual range detector with twelve incorporated trackers, as shown in Figure 10;
  • Fig. 13 shows the diagram of the operating principle of the residual range detector
  • Fig. 14a shows a schematic illustration of Q layers cross-sectioned
  • Fig. 14b shows the energy track of the particle passing through the Q layers
  • Fig. 14 is the basic drawing of a device for radiography of a volume with charged particles (protons) based on the principle of measurement of the residual range of the particles after crossing said volume; each proton, one at a time, is tracked before and after crossing a phantom, the volume of which is to undergo radiography; a residual range detector measures the energy of the proton by means of measurement of the Bragg peak, after crossing the phantom;
  • Fig.16a illustrates the attenuation of the luminous intensity I as a function of the variation in the distance travelled inside the fiber
  • Fig. 16b shows the diagram of the signals at the ends of a fiber
  • Fig. 17 shows the diagram of the mechanism for measuring the amplitude of the signals by means of counting of the time above the threshold
  • Fig. 18 shows a prototype realized using scintillating fibers where a single strip is rewound so as to form a sensitive area of given dimensions
  • Fig. 18d is a photograph of the prototype realized and the photographs 18a, 18b and 18c show, respectively, the strips folded in their final position as in the preceding Figures Fig. 8, Fig. 7 and Fig. 9
  • Fig. 19 shows the image of the profile of a proton beam, in two planes of the tracker, obtained by means of the prototype and acquired in real time, the units of the axes being fibers of 500 microns;
  • Fig. 20 shows in (a) a photograph of the test detector and in (b) and (c) the photographs of the layers viewed from the front and side, respectively;
  • Fig. 21 shows the graph of the position of the Bragg peak measured and simulated as a function of the initial energy of the particles with best-fit results.
  • a method for reducing the read-out channels of segmented strip detectors made using scintillating optical fibers is described.
  • d is the dimension of the fiber
  • the diameter in the case of fibers with a circular cross-section and the side size in the case of fibers with a square cross-section will be defined by N*d.
  • the number of optical channels necessary for extracting the position information from the detector is defined by N+M. If it is required to acquire the signal supplied at both the ends of the fibers in order to filter spurious signals, noise or interference, which are not time correlated with passing of the particle, by means of the time coincidence mechanism, 2*(N+M) read-out channels must be acquired.
  • the signals which are present "simultaneously" at the ends of the fiber struck, albeit with a different amplitude, will therefore be regarded as particle signals, the amplitude of the signal depending on the distance traveled by the light in the two opposite directions of the fiber.
  • the coincidence time interval T equal to the maximum time taken by the scintillation light to pass out of the fiber, with L, the length of the fiber, divided by the speed of the light in the fiber material, c*nf, with nf, the refraction index of the material from which the fiber core is made, a non-zero signal must be obtained at both the ends of the fiber within the time interval T (time coincidence).
  • a single strip at a time, for each direction (x and y), must provide non-zero information, namely, the person skilled in the art is able to define measurement conditions such that the particles cross the detector one at a time.
  • a detector able to measure the position and direction in which its sensitive area is crossed by a particle is called a tracker.
  • a tracker may be realized by combining the information of at least two position detectors. In fact, the straight line which joins together the crossing points of the two position detectors gives the direction of movement of the particle.
  • a position detector may be one-dimensional or two-dimensional depending on the number of coordinates of the point of its sensitive area crossed by the particle, which may be reconstructed by means of it.
  • the idea forming the basis of the invention consists in exploiting the light guiding properties of scintillating fibers in order to obtain a further reduction of the read-out channels required to extract the crossing position. By exploiting this property, as already mentioned, it is possible to obtain duplication of the channels since the light produced by crossing of a particle arrives at both the ends of the fiber.
  • the sensitive area or active area of the detector is the area where the strip is superimposed onto itself.
  • it is a right-angled triangle, as indicated in the figure by means of the area defined by broken lines.
  • Inside the dashed-line area there is superimposition of the two ends or portions of the strip which determines the form of the basic area, or pixels, of the detector.
  • a detail of the pixel structure is shown in Figure 5.
  • the strip of scintillating fibers suitably wound as shown in Figure 3 forms the elementary structure, or basic element, for construction of a position detector.
  • each fiber of the strip must not be superimposed completely onto itself in the active area
  • the bending radius must be at least equal to or greater than 100 times the dimension of the cross-section of the scintillating fiber (diameter in the case of fibers with a round cross-section or side size in the case of fibers with a square cross-section);
  • This angle a may be varied in the range 0 ⁇ a ⁇ 0° while satisfying at least one of the conditions 1 and 2. Where a is not equal to 0, condition 1 will not be satisfied; in this case the strip parts beyond the curvature will not be superimposed on each other, but be spaced from each other and substantially U-shaped as shown in Fig. 7. Superimposition of the fibers generates pixels, which represent the information relating to the impact position, in the form of a parallelogram, as shown in Figure 5.
  • superimposition is obtained with one strip only.
  • superimposition is obtained by placing two U-shaped strips in contact with each other and positioned orthogonally relative to each other. In this case the pixels will have a square form.
  • the form of the pixels created by superimposition of the strip onto itself has the form of a parallelogram, the dimensions of which are equal to about d*(d/senod. It should be noted how, by varying the angle a, it is possible to modulate the vertical resolution of the detection area, expressed as is known to the person skilled in the art, as the vertical dimension of the pixel divided by ⁇ ⁇ . The horizontal resolution, instead, remains fixed by the dimension of the cross-section of the fiber d divided by ⁇ 2.
  • the event generated by the passage of the particle across the sensitive area i.e. the useful detection area, produces four light signals in time coincidence (quadruple coincidence).
  • a schematic illustration of the coincidence is shown in Figure 4A.
  • the signals are detected by a number of sensors equivalent to that required to detect the single coincidence in the case of fibers which are not folded, this being half that the number of those which would be required in the case of two separate strips.
  • the technique of reducing the channels according to invention which consists in folding the strips as mentioned above, allows reconstruction of the coordinates of the impact point in quadruple coincidence without increasing the number of channels to be read.
  • the number of read-out channels for a tracker will be equal to the number required for a position detector, but the amount of information about the particle will be greater since information about its path will also be obtained;
  • a necessary condition is that the strips, after the curvature zone, should remain substantially parallel to each other, with an approximately U-shaped form.
  • the method and the system for extracting the crossing position of the two position detectors are similar to those of the preceding example.
  • a further advantage of this solution lies in the possibility of combining the various strips of scintillating fibers so as to form several tracking layers with the same reduction factor of the total read-out channels, i.e. 1/2, in quadruple coincidence conditions.
  • Fig. 9 shows the result of using 4 strips of scintillating fibers folded substantially in a U shape, as shown in Figure 7, so as to obtain a tracker consisting of a total of 4 position detectors.
  • two U-folded strips as shown in Figure 8 it is possible to form two bidimensional position detectors.
  • two sides will be used for curving of the strips and the remaining sides for grouping together the fibers.
  • the detector will therefore have a larger overall size, but in this case it will be possible to realize pixels of the position detectors which are square.
  • the time quadruple coincidence which is implicit in the reduction mechanism, allows the noise of the optical sensors to be eliminated.
  • a possible and advantageous application of the tracker construction method described hereinabove consists in the realization of a residual range detector.
  • a residual range detector may be realized, for example, by aligning Q layers of N scintillating fibers, parallel to each other and orthogonal to the direction of propagation of the particles.
  • the residual range detectors measure the distance traveled by the particle within them; they are therefore characterized by having a certain thickness organized in layers which may be realized with sheets of scintillating fibers or with plastic scintillation sheets arranged next to each other.
  • the residual range layers are not necessarily all identical to each other. As shown in Fig. 12, the residual range layers may consist of a different number and generally the particle energy is all the lower the smaller the overall thicknesses.
  • the distance travelled by the particle inside them is correlated to the initial energy of the particle, i.e. the energy before entry into the detector [4].
  • the charged particles which enter with angled trajectories into the detector will have a range (in terms of distance travelled inside the detector) which is different depending on the angle, this being calculated, in the absence of information about the trajectory, as though the latter were always perpendicular to the detection layers.
  • range in terms of distance travelled inside the detector
  • the possibility of tracking the particles inside the residual range detector allows the measurement of the energy distribution (range) and spatial distribution (beam profile) of each particle to be performed at the same time and in coincidence.
  • the layers of the residual range detector are understood as being formed with strips of scintillating optical fibers or with plastic scintillation sheets, the scintillation light of which, as a result of the loss of energy by particles, is collected and measured using methods known per se.
  • Figure 11 shows a tracking detector combined with a range detector in which each range detector is formed with groups of eight layers arranged between one position detector and the next one, giving a total of four tracker strips, arranged orthogonal to each other.
  • Grouping of the scintillating fibers may be performed in different ways. A number of possible methods of implementing grouping of the channels are described here; in this connection a channel is one of the two ends of a scintillating fiber.
  • each single group of scintillating fibers is optically and mechanically coupled to a photosensor
  • each single group of scintillating fibers is optically and mechanically coupled to a coaxial clear fiber having a cross- sectional area greater than the sum of the cross-sections of the scintillating fibers coupled thereto, or to a wavelength shifting (WLS) fiber.
  • the clear fibers or the WLS fibers are then optically and mechanically coupled to a photosensor;
  • the analog signal which is typically a high-speed current pulse, will then be suitably amplified, so as to optimize the signal/noise ratio, and then compared with a threshold by means of a comparator or converted into numerical format by means of an analog/digital converter.
  • a comparator or converted into numerical format by means of an analog/digital converter.
  • FIG. 14 A schematic representation of an apparatus for performing proton radiographs combined with range detectors is shown in Figure 14. Each proton, one at a time, is tracked before and after crossing a phantom.
  • the phantom corresponds to the volume on which the radiograph is to be performed.
  • the trackers detect the spatial coordinates of the proton entering and leaving the volume to be radiographed and the residual range detector measures its energy by means of measurement of the Bragg peak, after crossing the phantom.
  • radiograph is repeated by rotating the system of detectors axially around the phantom at predefined angles it is then possible to reconstruct the tomograph of the phantom.
  • the method of compressing the read-out channels according to the invention consists in applying a mathematical algorithm to the read- out channels of a segmented detector in order to reduce the number of read-out channels to be acquired, while keeping intact the information produced in the detector upon passing of the particle.
  • the method according to the invention is directly applicable to all the linear segmentation detectors based on scintillating fibers and may be adapted, using methods known to the person skilled in the art, to those of other technologies and allows their performance to be improved in terms of detection speed, costs and dead time acquisition.
  • the channel compression method according to the invention is based on the properties of the numbers, prime relative to each other, such that they are not mutually divisible.
  • p and ⁇ are two positive whole numbers ⁇ 0, prime relative to each other, namely such that, when divided, positive fractional numbers ⁇ 0 are obtained;
  • N is less than or equal to 5
  • N there is no reduction of the channels, although the method described above may still be applied, while if N is very high the compressed number of channels tends towards Therefore the method is understood as being useful for N>5, even though using channel compression makes sense only where N is much greater than 5.
  • the priority is to reach the minimum number of final channels (p+s).
  • the compression factor for a strip with N fibers is equal to where the strip is a flat strip, and 2 ⁇ , where the strip is folded according to the invention.
  • Figure 15 shows a diagram of a tracker realized by applying to the scintillating fibers the channel compression system described for measurement of only the x coordinate of the impact point.
  • the scintillating fiber 5 struck by the particle produces a signal on the compressed channels SGI and PG5.
  • Figure 16a shows the progression of the function I(x), while Figure 16b shows how the signals at the two ends of the scintillating fiber, of length L, differ owing to the attenuation and the different distance, L- d and d, travelled by the scintillation light from the impact point.
  • the channel compression method is applied taking into account the fact that the particle crosses the strip twice through the active area (as shown in Figure 3 and Figure 4A). Therefore at each end of the strip only two fibers will produce a non-zero signal in time coincidence upon crossing of a particle.
  • the detector will therefore provide a quadruple coincidence of signals representing events relating to the passage of particles, allowing exclusion of signals due to optical or electronic noise.
  • the smaller attenuation length namely the distance travelled by the light in the fiber where the initial luminous intensity is reduced to 1/e (e ⁇ 2.7 Napier's constant), is usually dominant in the range of lengths of interest in the construction of detectors (the maximum length of the fiber must be such as to provide a signal at both the ends for any point of the fiber crossed by the particle) and already at the output of the strip portion in which the curvature is provided, before bonding together the two strips at an angle a, the two signals are substantially different.
  • the optimal bending radius (lOOx) will be 5 cm, and the strip portion in the curvature will have a length equal to about 2n times the bending radius, namely 30 cm. This value is equal to about 3 times the lower attenuation length and, therefore, the attenuation introduced by the curvature is certainly greater than one third.
  • the length of the strip will be chosen so as to have a non-zero signal for any impact point and moreover, the signals output at the two ends of the strip will certainly have an amplitude which is different and a function of the distance travelled.
  • the SG and the PG groups according to the channel compression method, with each fiber N of the strip and determine the coordinates x and y of the impact point.
  • Two strips with N 600 scintillating fibers folded at an angle a and arranged as shown in Figure 8.
  • p and s are two positive whole numbers ⁇ 0, prime relative to each other, namely such that, when divided, positive fractional numbers ⁇ 0 are obtained;
  • the total number of read-out channels, applying the teachings of the invention is 98 (2 x 49) to be compared with the number of channels required, which, in order to obtain time quadruple coincidence in each plane XY, without using the teachings of the present invention, would be equal to 4800.
  • the compression factor for example B compared to example A is about 50, with a reduction of about 2 ⁇ .
  • Photosensor 64-anode multi-anode photomultiplier
  • PSPM Position Sensitive Photo-Multiplier
  • o Detector structure o Fiber support frames for sensitive area
  • o Acquisition board front-end adapter especially designed and made (INFN, Catania);
  • Sensitive area 30x30 cm 2 for two trackers in time quadruple coincidence
  • the channel compression method described in the preceding sections was applied to the fibers of each strip.
  • the method consists in suitably grouping the scintillating fibers at the two ends of each strip.
  • p and s are two positive whole numbers ⁇ 0, prime relative to each other, namely such that, when divided, positive fractional numbers ⁇ 0 are obtained;
  • the total number of read-out channels of the prototype is 98 (2 x 49) to be compared with the number of channels required, which, in order to obtain time quadruple coincidence in each plane XY, without using the teachings of the present invention, would be equal to 4800.
  • the compression factor is about 50.
  • the solution is to measure the signal amplitude in order to make use of attenuation, being dependent on the distance travelled by the scintillation light produced at the interaction point.
  • FIG. 17 illustrates the measurement mechanism in schematic form.
  • the scintillation light produced by crossing of the particle is propagated towards the two ends thereof and reaches the sensitive surface of a photosensor to which all the fibers of the same grouping, PG or SG, are optically coupled.
  • the photomultiplier will convert the light into an electric signal proportional to the number of scintillation photons.
  • the front-end board houses the photomultiplier and compares each of the 64 analog outputs with a single threshold, which can be adjusted remotely, by means of fast comparators.
  • the outputs of the 64 comparators are then sampled at 200 MHz by acquisition boards based on programmable logics [9].
  • each strip which are grouped according to the channel compression method described above, are coupled to a PSPM (Position Sensitive Photo-Multiplier) and therefore there are two front-end boards which are read simultaneously by an acquisition board.
  • PSPM Purpossition Sensitive Photo-Multiplier
  • the acquisition boards which continuously sample the outputs of the front-end boards, are programmed to store only the data in quadruple time coincidence, to analyze them and to send the data to a real-time calculation system for subsequent storage, processing and display.
  • Figure 18 shows on the left-hand side a photograph of the prototype realized and on the right-hand side the designs of the single strips [Figures 18(a) and 18(b)] and the strips in their final position [Figure 18(c)].
  • Figure 19 shows the image of the profile of a proton beam with a diameter of 3.5 cm, in the two planes of the tracker, obtained by means of the prototype and acquired in real time.
  • the units are the dimension of the cross-section of the scintillating fibers, 500 um.
  • the image is acquired one proton at a time at a rate of about 3 MHz.
  • This detectors consist of layers of scintillating fibers BCF-12 with a square cross-section of side size 500 um read by means of WLS (Wavelength Shifting) fibers BCF-92a.
  • the 60 layers equivalent to 3 cm of water, capable of stopping protons with energy up to 60 MeV, are positioned and aligned in an aluminum support structure.
  • the WLS fibers of each layer are optically coupled to a 64-anode PSPM.
  • the PSPM is housed on a front-end board identical to that illustrated above for the tracker prototype.
  • the two detectors have, namely, the same acquisition system.
  • the first expected result was a good agreement between the simulations and the measurements carried out under the proton beam.
  • the application of the channel compression method used was simulated by means of software and it was shown that the results with or without compression are identical. After application of the compression method the number of resultant channels is 16 channels.
  • Using the same front-end and acquisition system it would therefore be possible to realize a large-area and high-resolution residual range detector and, in particular, cover a range of particles up to 50 cm (1024 layers of fibers of size 500 um) sufficient to stop completely the protons at the energies used for imaging, about 250 MeV. In this case the protons must pass through the body, releasing the minimum dose possible without stopping.
  • Figure 20 shows in (a) a photograph of the test detector and in (b) and (c) the photographs of the layers viewed from the front and side, respectively.
  • Figure 21c shows the layer of scintillating fibers with a square cross-section through one of the WLS fibers.
  • Fig. 21 shows a graph of the position of the Bragg peak measured and simulated as a function of the initial energy of the particles. The data of the measurements and simulated data were then compared with the law which provides the Bragg peak as a function of the kinetic energy of the particle. The units along the y axis are the 500 urn layers.
  • FAST A COMPACT SCINTILLATING FIBER DETECTOR FOR ANTIPROTON CROSS SECTION MEASUREMENTS (WSPC - Proceedings - November 2007);

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Abstract

La présente invention concerne des détecteurs à bande segmentée de particules chargées, dans lesquels les bandes comprennent une ou plusieurs fibres de scintillation et les fibres sont agencées sous la forme d'une bande et sont pliées sur elles-mêmes de manière à former une boucle ayant un rayon de cintrage qui est ≤ 100 fois le diamètre ou la dimension latérale, dans le cas de sections transversales carrées, et la bande est pliée de telle sorte que ses parties terminales forment un angle de 0 ≤ α ≤ 90° au-delà de la courbure, lesdites parties terminales étant superposées dans le cas où l'angle est α ≠ 0 ou parallèles et espacées dans le cas où α = 0. Ces détecteurs peuvent être des détecteurs de position ou des détecteurs de suivi monodimensionnels ou bidimensionnels et peuvent être combinés avec des détecteurs de plage résiduelle. La présente invention concerne également une compression du nombre de canaux de lecture de ces détecteurs obtenus au moyen d'un regroupement approprié des fibres au niveau des deux extrémités de lecture de celles-ci, obtenant un facteur de compression égal à 2·√N, N = le nombre de canaux de lecture des fibres, en coïncidence quadruple. Les détecteurs selon la présente invention sont aptes à être appliqués à un appareil pour radiographie ou tomographie utilisant des particules chargées.
PCT/IT2013/000168 2012-06-12 2013-06-12 Détecteur basé sur fibres optiques de scintillation pour suivi de particules chargées ayant une application dans la réalisation de détecteur de plage résiduelle employant un procédé de compression et de réduction de canaux de lecture WO2013186798A2 (fr)

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IT000273A ITRM20120273A1 (it) 2012-06-12 2012-06-12 "metodo di compressione e riduzione dei canali di read-out e sua applicazione per la realizzazione di un sistema di indagine per particelle cariche, in tempo reale, di grande area ed alta risoluzione spaziale"
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US9977136B2 (en) 2014-02-03 2018-05-22 The Arizona Board Of Regents On Behalf Of The University Of Arizona Beta and alpha emission tomography for three-dimensional autoradiography
EP3102966A4 (fr) * 2014-02-03 2017-10-11 The Arizona Board of Regents On Behalf of the University of Arizona Tomographie par émission bêta et alpha pour une autoradiographie tridimensionnelle
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EP3298434B1 (fr) * 2015-05-19 2022-11-16 Protonvda Inc. Système d'imagerie protonique pour l'optimisation d'une thérapie protonique
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JP2018524043A (ja) * 2015-05-19 2018-08-30 プロトンブイディーエー インコーポレイテッド 陽子療法の最適化のための陽子撮像システム
US11684328B2 (en) 2015-05-19 2023-06-27 Protonvda Llc Proton imaging system for optimization of proton therapy
EP4148466A1 (fr) * 2015-05-19 2023-03-15 Protonvda Inc. Système d'imagerie protonique pour l'optimisation d'une thérapie protonique
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US11116459B2 (en) 2015-05-19 2021-09-14 Protonvda Llc Proton imaging system for optimization of proton therapy
JP2021183144A (ja) * 2015-05-19 2021-12-02 プロトンブイディーエー エルエルシー 陽子療法の最適化のための陽子撮像システム
WO2016187447A1 (fr) * 2015-05-19 2016-11-24 Protonvda Inc. Système d'imagerie protonique pour l'optimisation d'une thérapie protonique
CN106908831A (zh) * 2017-03-28 2017-06-30 中国科学院高能物理研究所 基于微结构阵列的粒子径迹探测装置
JP2021509468A (ja) * 2017-12-28 2021-03-25 ボード オブ トラスティーズ オブ ノーザン イリノイ ユニバーシティー 即時粒子画像再構築のための処理パイプライン
US10918350B2 (en) 2017-12-28 2021-02-16 Board Of Trustees Of Northern Illinois University Processing pipeline for prompt particle image reconstruction
WO2019133678A1 (fr) * 2017-12-28 2019-07-04 Board Of Trustees Of Northern Illinois University Pipeline de traitement pour reconstruction rapide d'image de particules
US11813105B2 (en) 2017-12-28 2023-11-14 Board Of Trustees Of Northern Illinois University Processing pipeline for prompt particle image reconstruction

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