Organization legal name	Short name	Activity leaders
Österreichische Akademie der Wissenschaften	OeAW	J. Zmeskal
Istituto Nazionale di Fisica Nucleare	INFN
INFN Sezione di Bari	INFN-BA	A. Ranieri
INFN Laboratori Nazionali di Frascati	INFN-LNF	G. Bencivenni/C.Curceanu
Gesellschaft für Schwerionenforschung mbH	GSI	B. Voss/C.J. Schmidt
Technische Universität München	TUM	B. Ketzer
Helsingin yliopisto	UH	F. Garcia
Institutul National de Cercetare	IFIN-HH	M.Bragadireanu
University of Glasgow	UGlasgow	J.Annand
Variable Energy Cyclotron Center (India)		S. Chattopadhyay
Petersburg Nuclear Physics Institute, Gatchina (Russia)		V.Nikulin

The next generation of experiments in hadron physics aims at studying rare processes with drastically improved sensitivity. The technical requirements to reach this goal include high beam intensities and luminosities, fast detectors with large acceptance and high resolution. Examples are, among others, the KLOE2 and AMADEUS experiments at DAFNE-LNF, Frascati, Italy, and PANDA and CBM at FAIR, Darmstadt, Germany. An essential part of all these experiments is a detector for charged particles with excellent tracking capabilities covering large areas or volumes with an extremely low material budget in order not to spoil the energy and mass resolution of the apparatus. In addition a rate capability matching the envisaged high luminosities is required.

Micropattern Gas Detectors (MPGD) based on the Gas Electron Multiplier (GEM) technology provide a very promising path towards these goals. Within this JRA we plan to study and develop prototypes of a number of innovative detectors far beyond the current state-of-the-art:

• a high-rate Time Projection Chamber (TPC) with GEM readout, as planned for the inner tracker of PANDA at FAIR;

• a multilayer self-supporting cylindrical GEM (C-GEM) structure, as foreseen for

AMADEUS and KLOE2;

• large-area planar GEM detectors capable of withstanding very high beam rates, as envisaged for the forward tracking system of PANDA and for the muon system of CBM.

All these detectors have very similar stringent requirements originating from the physics goals of the respective experiments:

• active areas of the order of m²,

• spatial resolutions of ~100 μm to 500 μm,

• time resolutions of the order of a few ns,

• low material budget inside the active area, 1.5 % of a radiation length for the whole tracking detector,

• rate capability up to several tens of kHz per mm2.

In order to achieve the above-mentioned goals, the research activities will focus on three projects.

 

1. TPC-GEM

After the successful construction and operation of a small-size TPC-GEM as a first stage, a prototype chamber will be built to proof the principle on a larger scale. For this a TPC with a drift length of 50 cm, an inner radius of 10 cm, and an outer radius of 30 cm is envisaged. It will be built making use of the lightest possible materials, as well as close-to-final readout electronics. Apart from serving as a prototype for the PANDA TPC, this TPC, if successful, is foreseen to be installed and used for physics already in other hadron physics experiments, e.g. FOPI at GSI, and Crystal Barrel at ELSA.

 

2. Cylindrical-GEMs

We plan to develop a novel ultra-light, fully cylindrical and dead-zone-free triple-GEM detector as inner tracker. The final detector will be composed of five concentric layers, each one represented by a cylindrical triple-GEM detector (C-GEM). Each cylindrical structure is made of thin (50÷100 μm) polyimide foils: the cathode, the three GEMs and the anode readout. Due to the overall detector dimensions - layer diameters in the range 300÷500 mm with corresponding lengths of about 400÷600 mm - very large GEM foils, up to 600×1500 mm2, are required. In addition, we will study the use of a suitable stretching technique applied on the cylindrical structures comprising each detector, which will permit to avoid support frames inside the detector active area.

 

3. Large area planar GEMs

In addition to the central tracking of charged particles by a cylindrically-shaped detector as described above, tracking in the outer or forward regions of high-rate experiments requires light detectors which can withstand very high particle rates up to several tens of kHz per mm2. Even with a reduced bending power of the magnetic field in these regions, the high spatial resolution achievable with GEM detectors allows to achieve the required momentum resolution. In PANDA, large planar GEM detectors will be employed for the forward tracking inside the target spectrometer. Depending on the acceptance of the central tracker and the distance to the interaction point, the forward trackers have to be much larger than present-day MPGDs. A reduced thickness of the copper cladding and very light-weight frames are a prerequisite for this application. Due to the fixed-target nature of the experiment, the readout structure close to the beam has to consist of individually read out pixels. Further outside where the occupancy is lower, a strip readout can be envisaged in order to limit the number of readout channels. This requires multi-layer, very thin readout printed circuit boards incorporating both the structures for signal induction and the routing to the front-end electronics. A first small-size prototype of such a structure has been successfully manufactured and tested in 2006 for the COMPASS beam tracking, showing very promising results in terms of resolution and rate capability.

 

The three projects are broken down into five smaller tasks:

• Development of thin large-area GEM (led by GSI),

• Development of large-area read-out structures (led by TUM),

• Quality control and calibration (led by UH),

• Material research (led by OeAW),

• Light-weight frames and support structures (led by INFN-LNF),

 

The interdependencies and relations of the individual tasks have been established. The work to be performed within the five tasks is essential for the success of all three sub-projects, thus the synergy effect is clearly visible.

The leading institutions in the project are OeAW, INFN-LNF, TUM and GSI, where extensive experience in this field exists from former investigations. The other groups bring in their specific experiences in various fields, e.g. electronics design.

Task No.	Tasks	Deliverable	Deliverable month from start date
1	Study of techniques to produce large area GEM foils	Report on production techniques	30
2	Development of large read-out structures	Design study	30
3	Quality control and calibration	Report on process description	30
4	Material research	Database of materials	30
5	Light-weight frames and support structures	Report for each sub-project	30

The outcome of the project will strongly influence the design and construction of tracking devices in hadron and particle physics. It is also of interest for future applications in other fields, like astrophysics and medical applications. It will bring nearer together many European groups working in this field and will influence the detector groups working in the infrastructures of this proposal.

 

In particular, the following aims will be tackled:

• Study to develop thin, large-area (~500x1000 mm2) GEM foils. The present two-mask lithography is not suited for this task since the precision required for both masks cannot be maintained over large areas. New precision patterning and etching techniques have to be evaluated, e.g. single-mask etching and laser-direct imaging. In addition gluing of GEM foils with minimal dead regions will be studied. The thickness of the Cu layer can be reduced either a posteriori by chemical etching, or by reducing the vacuum deposited Cu layer on the raw polyimide material.

• Development of thin, flexible and large-size read-out structures with high granularity, using Kapton technology. Here we will concentrate on the development and the optimization of the manufacturing process, on the development of hybrid structures with combined pixel and strip readout matching the expected occupancies, and on the optimization of the readout patterns and the signal routing.

Stringent quality control throughout the manufacturing process is essential for the reliability of the resulting detectors. New techniques automated for electrical and optical inspection and the mapping of the gain uniformity have to be developed.

• Development of extremely light-weight frames and support structures, with large radiation lengths. Not only the active components, but also the support structure materials of the detector have to be as light as possible. New materials for frames and support structures will be searched for and characterized in terms of their applicability for particle detectors.

P-3	Large Area GEM	B.Voss (GSI)
Sub-project	Name	Sub-project leader
P-1	TPC-GEM	B.Ketzer (TUM)
P-2	Cylindrical-GEM	G.Bencivenni (LNF)

Tasks	Name	Task leader
T-1	Study of techniques to produce large area GEM foils	GSI, LNF
T-2	Development of large read-out structures	TUM
T-3	Quality control and calibration	HIP
T-4	Material research	SMI
T-5	Light-weight frames and support structures	LNF, GSI