Fiber Detector Research Articles

Elastic arms for track reconstruction with a scintillating fiber detector

The elastic arm method is applied to track reconstruction in a scintillating fiber tracker for use in future detectors (LEP II, LHC). Raw data were pre-processed to produce microvectors which will constitute the input to the elastic arm algorithm. Results show good track reconstruction over 100 events and covering more than one thousand tracks.

Experience with position-sensitive photomultipliers from the H1 forward proton spectrometer

For the H1 experiment at the HERA accelerator we built high resolution fiber detectors to measure very forward produced protons escaping the central H1 detector through the beam pipe. The fiber detectors were installed in movable vertical vacuum inserts, so-called Roman pots, touching the beam envelope at distances of 81 m and 90 m from the interaction point. The detection of the scintillation signals is performed by four position-sensitive photomultipliers H4139 per Roman pot. An approved upgrade program foresees the installation of additional stations at 63 m and 80 m. For the fiber readout another type of PSPM based on micro-channel plates is envisaged.

MRS detectors with high gain for registration of weak visible and UV light fluxes

Operation of silicon avalanche detectors based on a Metal-Resistive layer-Semiconductor (MRS) structure is presented. Results refer to a new batch of detectors fabricated on a n-type substrate especially made to be used as light detecting elements of a scintillating fiber detector for high energy physics applications. These detectors are meant for weak light fluxes in the range 200–600 nm (called UV MRS). Measurements of gain, noise and quantum efficiency were performed and operation of the detector at different temperatures was also studied.

Predictions and measurements of scattering and absorption over broad wavelength ranges in tissue phantoms

Predictions from Mie theory regarding the wavelength dependence of scattering in tissue from the near UV to the near IR are discussed and compared with experiments on tissue phantoms. For large fiber separations it is shown that rapid, simultaneous measurements of the elastic scatter signal for several fiber separations can yield the absorption coefficient and reduced scattering coefficient. With this information, the size of the scattering particles can be estimated, and this is done for Intralipid. Measurements made at smaller source detector separations support Mie theory calculations, demonstrating that the sensitivity of elastic scatter measurements to morphological features, such as scatterer size, is enhanced when the distance between the source and detector fibers is small.

Development of an encapsulated scintillating fiber detector as a 14-MeV neutron sensor

A scintillating fiber detector has been developed and tested for use as a 14-MeV neutron sensor. The detector, designated an “Encapsulated Scintillating Fiber Detector (EFD)”, is composed of a parallel array of 0.5 × 0.5 × 15 mm BCF-12 plastic scintillating fibers encapsulated in clear BC-600 optical cement. The 85 fibers from a 12 × 12 mm square array, with a separation gap of 0.8–1 mm, in the center of the 40 mm diameter × 15 mm thick hardened optical cement. It can be directly coupled to an ordinary 2 in. diameter photomultiplier tube and its simple electronics. The response of the detector to gamma-rays from isotopic sources, as well as to 2.6- and 14-MeV monoenergetic neutrons from a neutron generator has been evaluated. The detector shows 3 distinct properties simultaneously, i.e. (1) good gamma-ray pulse height reduction, (2) discrimination against 14-MeV neutrons entering at angles non-parallel to the fiber axis, and (3) production of a full energy peak of 14-MeV recoil protons in the direction of the fiber axes. Investigations by Monte Carlo simulation are also included.

185. シンチレーションファイバー検出器アレイを用いる電子線の深部吸収線量分布計測システムの開発

185. シンチレーションファイバー検出器アレイを用いる電子線の深部吸収線量分布計測システムの開発

波長664nm半導体レーザ光を用いた生体組織内ME2906の吸収係数の測定

The light distribution in vivo during Photodynamic Therapy is dependent on a pre-administered photosensitizer in the target tissue. To discuss the light absorption of photosensitizer (ME2906), the light distribution in normal muscle at 664nm was measured with optical detector fiber. From this distribution, the absorption coefficient of ME2906 in tissue was calculated. As an optical source, a semiconductor laser is prepared. The incident laser beam diameter at the tissue surface is 10mm, and the power density was 100mW/cm2. In proportion as the concentration of ME2906 increases, absorption coefficient of ME2906 increases in the range from 0.06 to 0.16mm-1. This coefficients are related to ME2906 concentrations in the plasma and tissue. Therefore, ME2906 concentrations of plasma were examined by high-performance liquid chromatography (HPLC).

DQE measurement in a scintillating glass optical fiber detector for X-ray imaging

An example of the measurement of detective quantum efficiency is illustrated for a scintillating glass optical fiber detector used in X-ray imaging. We have shown the necessity to filter the input Poisson noise of the incoming beam, by the MTF (Modulation Transfer Function) of the detector, in order to obtain the real DQE (Detective Quantum Efficiency).

Beam tests of prototype fiber detectors for the H1 forward proton spectrometer

Abstract Different prototypes of fiber detectors with an internal trigger system were tested in a 5 GeV electron beam at DESY. A silicon microstrip telescope was used for an external reference measurement of the beam to study the spatial resolution of the fiber detectors. On average 75% of all crossing electron tracks could be reconstructed with a precision better than 150 μm. These successful methodical investigations led to the installation of similar detectors in the proton beamline 81 m downstream of the central H1-detector at HERA as part of a forward proton spectrometer in spring 1994.

The sensitivity of normal brain and intracranially implanted VX2 tumour to interstitial photodynamic therapy.

The applicability and limitations of a photodynamic threshold model, used to describe quantitatively the in vivo response of tissues to photodynamic therapy, are currently being investigated in a variety of normal and malignant tumour tissues. The model states that tissue necrosis occurs when the number of photons absorbed by the photosensitiser per unit tissue volume exceeds a threshold. New Zealand White rabbits were sensitised with porphyrin-based photosensitisers. Normal brain or intracranially implanted VX2 tumours were illuminated via an optical fibre placed into the tissue at craniotomy. The light fluence distribution in the tissue was measured by multiple interstitial optical fibre detectors. The tissue concentration of the photosensitiser was determined post mortem by absorption spectroscopy. The derived photodynamic threshold values for normal brain are significantly lower than for VX2 tumour for all photosensitisers examined. Neuronal damage is evident beyond the zone of frank necrosis. For Photofrin the threshold decreases with time delay between photosensitiser administration and light treatment. No significant difference in threshold is found between Photofrin and haematoporphyrin derivative. The threshold in normal brain (grey matter) is lowest for sensitisation by 5 delta-aminolaevulinic acid. The results confirm the very high sensitivity of normal brain to porphyrin photodynamic therapy and show the importance of in situ light fluence monitoring during photodynamic irradiation.

185.シンチレーションファイバー検出器アレイを用いる電子線の深部吸収線量分布計測システムの開発(第24回秋季学術大会 一般研究発表予稿集)

185.シンチレーションファイバー検出器アレイを用いる電子線の深部吸収線量分布計測システムの開発(第24回秋季学術大会 一般研究発表予稿集)

Slow neutron beam diagnostics with a scintillating fiber detector

A slow neutron-sensitive scintillating glass optical fiber plate is coupled to an intensified CCD camera, working at standard TV rate and room temperature, for beam positioning and spatial distribution diagnostics. Results are reported about a thermal neutron beam, in the presence of a high gamma-ray background, which is removed by digital image subtraction.

A simple optical fiber axial speed detector

An optical fiber detector is developed to measure simply and accurately the axial speed of the plasma sheath in a plasma focus device. Using a suitable model, self-consistent information on the distribution of ionized mass and current inside the structure of the plasma sheath may also be inferred. The thickness of the sheath is also obtained.

Scintillating fiber detector performance, detector geometries, trigger, and electronics issues for scintillating fiber tracking

Scintillating fiber tracking technology has made great advances and has demonstrated great potential for high speed charged particle tracking and triggering. The small detector sizes and fast scintillation fluors available make them very promising for use at high luminosity experiments at today's and tomorrow's colliding and fixed target experiments where high rate capability is essential. This paper will discuss the current state of scintillating fiber performance and current Visual Light Photon Counter (VLPC) characteristics. The primary topic will be some of the system design and integration issues which should be considered by anyone attempting to design a scintillating fiber tracking system which includes a high speed tracking trigger. Design constraints placed upon the detector system by the electronics and mechanical sub-systems will be discussed. Seemingly simple and unrelated decisions can have far reaching effects on overall system performance. SDC and D0 example system designs will be discussed.

A neutron spectrometer for ITER

A study of energy resolution and efficiency of a self-contained time-of-flight energy spectrometer has been performed by means of Monte Carlo calculations. For 14-MeV neutrons, the instrument provides an energy resolution of 225 keV, an efficiency of 10−3 cm2 and a neutron flux operating range from 5×106 to 1010 n/(cm2 s). For diagnostics of deuterium–tritium plasmas in ITER, measurements of ion temperatures ranging from 3 to 50 keV, with an accuracy better than 10%, a time resolution better than 100 ms and a radial resolution better than 5 cm are feasible. Usage of scintillating fiber detectors permits operation with background radiation levels well above those estimated for the diagnostic areas of the ITER experiment.

A directional fast neutron detector using scintillating fibers and an intensified CCD camera system

We have been developing and testing a scintillating fiber detector (SFD) for use as a fast neutron sensor which can discriminate against neutrons entering at angles non-parallel to the fiber axis (“directionality”). The detector/convertor component is a fiber bundle constructed of plastic scintillating fibers each measuring 10 cm long and either 0.3 mm or 0.5 mm in diameter. Extensive Monte Carlo simulations were made to optimize the bundle response to a range of fast neutron energies and to intense fluxes of high energy gamma-rays. The bundle is coupled to a set of gamma-ray insensitive electro-optic intensifiers whose output is viewed by a CCD camera directly coupled to the intensifiers. Two types of CCD cameras were utilized: 1) a standard, interline RS-170 camera with electronic shuttering and 2) a high-speed (up to 850 frame/s) field-transfer camera. Measurements of the neutron detection efficiency and directionality were made using 14 MeV neutrons, and the response to gamma-rays was performed using intense fluxes from radioisotopic sources (up to 20 R/h). Recently, the detector was constructed and tested using a large 10 cm by 10 cm square fiber bundle coupled to a 10 cm diameter GEN I intensifier tube. We present a description of the various detector systems and report the results of experimental tests.

Test of fiber detector readout by position-sensitive photomultipliers

Two fiber detectors consisting of round and square 0.5 mm scintillating fibers were exposed to a 5 GeV electron beam at DESY. The fiber readout was performed by two position-sensitive photomultipliers H4140 and XP1724 with 256 and 96 channels, respectively. The tracking efficiency and spatial resolution of these systems have been studied.

Development of silicon micropattern pixel detectors

Successive versions of high speed, active silicon pixel detectors with integrated readout electronics have been developed for particle physics experiments using monolithic and hybrid technologies. Various matrices with binary output as well as a linear detector with analog output have been made. The hybrid binary matrix with 1024 cells (dimension 75 μm×500 μm) can capture events at ∼5 MHz and a selected event can then be read out in < 10 μs. In different beam tests at CERN a precision of 25 μm has been achieved and the efficiency was better than 99.2%. Detector thicknesses of 300 μm and 150 μm of silicon have been used. In a test with a 109Cd source a noise level of 170 e − r.m.s. (1.4 keV fwhm) has been measured with a threshold non-uniformity of 750 e − r.m.s. Objectives of the development work are the increase of the size of detecting area without loss of efficiency, the design of an appropriate readout architecture for collider operation, the reduction of material thickness in the detector, understanding of the threshold non-uniformity, study of the sensitivity of the pixel matrices to light and low energy electrons for scintillating fiber detector readout and last but not least, the optimization of cost and yield of the pixel detectors in production.

Position-sensitive fiber readout

The possibility has been investigated to separate the signals from scintillating fibers in a fiber detector array by optical delay, thus providing the possibility to read-out several fibers with a single photomultiplier. Measuring basic fiber properties of PS and PMMA fibers, in particular the propagation and dispersion of light pulses we found that a separation of up to ten adjacent fibers can be achieved by optical delay. Limits of this method have been discussed and ways to improve the present limits have been indicated.

Fiber optic spectrometers for in-situ measurements in the oceans: the ZAPS Probe

The fiber optic spectrometers developed in this laboratory combine the power of a xenon flash source and the sensitivity of a photomultiplier detector with the flexibility of bifurcated fused silica lightguides. In the ZAPS (zero angle photon spectrometer) instrument optical interference filters are used to select wavelengths with source and detector fibers terminating in the same polished surface. ZAPS is a versatile light-processing instrument with a 6000 m capability. This report describes ZAPS deployments as a UV fluorometer and chemical sensor. As a fluorometer ZAPS can excite and detect violet fluorescence (FLU) from dissolved organic matter with the flash lamp and PMT filtered at 320 and 420 nm. A profile of FLU generated in situ with the ZAPS Probe is nutrient-like, increasing with depth below the euphotic zone. These results are consistent with previous measurements using shore-based instruments. ZAPS can be deployed as a chemical sensor. A technique developed for ZAPS makes it possible to determine dissolved Mn in the oceans in situ and in real time. The chemical method relies on the fact that reduced Mn in the presence of periodate has a catalytic effect on the oxidative coupling of fluorescent N,N′-diethylaniline (DEA) molecules producing the non-fluorescent product N,N,N′,N′-tetraethylbenzidine (TEBOx). In the ZAPS technique a pump pulls seawater through 2 chemical cartridges arranged in tandem with a flow-cell. The first cartridge contains retained periodate and the second bound DEA. The sample stream leaves the cartridges with micromolar levels of these reagents and is irradiated with UV light (250 nm) in the flow-cell. The level of fluorescence detected in the flow-cell is indirectly related to the concentration of Mn. The fluorescent response to Mn is linear over at least three orders-of-magnitude in concentration and the detection limit less than 0.1 nM. Seawater Mn profiles developed with this sensor are presented for an open-ocean station in the North Pacific and a hydrothermal vent site on the Gorda Ridge.