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• Significant enlargement of the availability, specifications and geometrical dimensions of inorganic scintillator materials shaped as optical fibers.
• Design, development and realization of new detector concepts based on inorganic scintillating fibers.
• Development of radio-frequency phototubes for extremely fast timing applications.

Scintillation detectors based on inorganic materials have become one of the most widely applied instrumentation techniques in physics – in particular in the fields of nuclear, hadron and high-energy physics. The increase of the energy regime of detectable probes directed crystal development towards faster response, shorter decay times, higher compactness implementing high-Z ions and radiation hardness. In contrast, plastic scintillator materials allow a nearly unlimited variation of geometrical shapes, even thin and very flexible fibers with optical coating. However, the properties are limited with respect to decay time and efficiency, which is in favor of the detection of charged particles due to the low Z-value of the organic molecules. Initiated by the recent experience, the proposal is focusing on the development of scintillating fibers based on inorganic materials.

They will provide significantly higher light yield as well as stronger interaction with electromagnetic probes due to the content of high-Z elements. In the last few years new Ce-doped scintillator materials have been developed based on Lanthanum chlorides and bromides. These scintillators reach energy resolutions for low energy gamma rays close to the theoretical limit and presently represent the optimum detectors in low energy spectroscopy. However, the commercial production has focused on medical and radiation monitoring applications due to the up to now small and medium crystal sizes. Those scintillators do not reach the compactness of PWO or LYSO, but they can also handle high count rates and provide sub nanosecond timing due to the fast decay time determined by Cerium. In addition, the use of photo sensors based on semiconductors favors scintillators, which predominantly emit the luminescence light at wavelengths well above the typical blue region near 400nm. In that case quantum efficiencies close to 60-80% could be fully exploited.

Therefore, there is a big challenge and opportunity, to produce – depending on the individual applicability – optimum scintillator candidates as well in the special shape as fiber with an appropriate optical cladding.

High granularity, large light-output and good radiation hardness will allow to cope with high-intensity and high-energy beams and could be installed in front of the experiment. Such an improved position sensitive device with high granularity could serve in case of good time resolution as a high-resolution start detector for time-of-flight measurement, readout via Multi-Anode photomultipliers or APD-arrays to cope with maximum count rates.

Fast and radiation hard start and trigger detectors are required in a wide field of accelerator experiments. As an example, in case of photon detectors or calorimeter elements, an inorganic fiber grid would allow for the first time to study position dependence of the detector response or define the point of impact of photons with sufficient efficiency and accuracy. Both applications are optimum tools for calorimeter developments.

Compact gas detectors for charged particle tracking, such as a time projection chamber (TPC) rely on a time reference. As an example, for the upgrade of the Crystal Barrel detector at ELSA, Bonn, a fiber array arranged along a cylindrical surface containing the envisaged TPC will deliver based on a fast double-sided readout position, time and energy loss information. Individual SiPMs are ideal for a compact readout within a strong magnetic field.

The proposed radio-frequency phototube (RFPMT) technique combines features of circular-scan streak cameras and regular photomultipliers. It can in principle provide fast, nanosecond signals for event by event processing of each photoelectron or secondary electron, produced in the photocathode, with better than 20 ps r.m.s. resolution. Such a phototubes, in combination with Cherenkov (or suitably fast scintillator if existing) could offer substantial improvements in timing precision compared to the detectors using conventional phototubes.

Sub-task 1.1 Development of the technology for fiber production: performed in collaboration between CNRS/LPCML and FIBERCRYST. The characterization is determined mainly by JLU and FIBERCRYST.

Sub-task 1.2 Production of fibers of new materials: primarily realized by FIBERCRYST.

Sub-task 2.1 Development of different concepts for fast start and trigger detector: design concepts are developed under the leading position of JLU with contributions from RUB, RuG, UU and UMainz.

Sub-task 2.2 Test and application of a position sensitive trigger detector for electromagnetic probes: detector tests to be performed at MAMI and MAX-LAB organized by JLU, supported significantly by RUB, UU and UMainz.

Sub-task 2.3 Test and application of a position sensitive trigger detector for charged particles: detector tests to be performed at MAMI and KVI, primary partners are RuG, RUB and UMainz.

Sub-task 3.1 Design of a cylindrical trigger detector for a compact TPC: development is directed by UBO in collaboration with JLU, RUB and CNRS/LPCML.

Sub-task 3.2 Test and application of a cylindrical start and trigger detector for charged particles: final tests and applications will be performed at ELSA under the supervision of UBO.

Sub-task 4.1 Development and pre-production of a radio-frequency phototube and first performance tests. The task is directed by University of Glasgow in close collaboration with the Yerevan Physics Institute.

New and innovative detector material for future instrumentation. Improvement of present technologies.

Supported by the wide applicability of inorganic scintillators, the availability of such materials as optical fibers will open up a new field of detector instrumentation. High-resolution calorimetry for the future ILC and upgrades at LHC considers concepts of practically digital readout of sampling calorimeters. One direction of R&D follows up an intrinsic identification and discrimination of hadronic and electromagnetic probes by a spaghetti-like detector with fiber readout using two materials such as quartz and plastic. Due to the limited radiation hardness of plastic fibers, inorganic materials would be superior.

In addition, those fibers would become very versatile detector components in compact medical tomography with the requirement on high granularity.

The new and innovative detectors concepts and prototypes for medium and high-energy applications should also cause an impact on modern read-out concepts and medical applications. The achieved performance of the selected prototypes is expected to initiate a new line in instrumentation.