Minutes of nustar calorimeter Working Group Friday 17th June 2005-06-17 Valencia, Spain Presents




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Minutes of NUSTAR calorimeter Working Group

Friday 17th June 2005-06-17

Valencia, Spain
Presents: J.Gerl,Y. Blumenfeld, A. Maj, J.Benlliure, T. Martinez, D. Cano, S. España, D.Cortina, I. Durán, J.L. Taín, M. Labiche, T. Aumann, T. Nilson, J.M Udias, K. Spohr, H. Alvarez, T.Feastermann, J. Díaz, W. Korten, M Turrión.

Agenda


Presentation of the different calorimeters

H. Alvarez (Universidad de Santiago de Compostela)

  • Status of the EXL calorimeter

Y. Blumenfeld (IPN Orsay)

J.L Tain (IFIC Valencia)

  • Status of the DESPEC calorimeter

J.L Tain (IFIC Valencia

Crystals and related topics

 J.Gerl (GSI Darmstadt)

Electronics: Ideas for VFEE



I.Duran (Universidad de Santiago de Compostela)

Simulations



H. Alvarez (Universidad de Santiago de Compostela)

S. España (Universidad Complutense de Madrid)
You may find the presentations in our web page http://www.usc.es/genp/r3b

in the calorimeter section.


The main goal of this meeting was to define synergies between the different groups inside the NUSTAR collaboration interested by the construction of a calorimeter.



The meeting started with the presentation of the different calorimeter concepts.
H. Alvarez (Santiago de Compostela, Spain) reported on the latest news regarding the R3B calorimeter design. The proposed solution consists on a detector covering a polar angle between 7-133o and divided in ~7000 crystals. This detector will be subdivided in three sub-detectors. The crystal segmentation yields an energy resolution (due to the polar angle segmentation) in the order of 3.5% and a total absorption efficiency in the order of 80%. The most plausible option for the scintillation crystal will be CsI. In this case the total detection volume would represent 363600 cm3 and 1600 Kg weight. You may find additional information on this design in the web page http://fpsalmon.usc.es/r3b/reports/report_cal_0105.pdf
Y. Blumenfeld (IPN Orsay, France) reported on the calorimeter for EXL. The specifications are the same that appear in the TP and quite similar to the R3B. The main differences between both detectors are the internal radius that increases up to 1 m in the EXL concept together with smaller azimuthal segmentation. Y. Blumenfeled presented the IPN groups that would participate in the project: the nuclear structure group leaded by himself and deeply involved in the construction of the MUST2 array for charged particle together with the Saclay group leaded by E. Pollaco and the detector group leaded by J. Pouthas and with a large experience in design and construction of detectors (particularly the calorimeters DVCS/CLAS at Jefferson Lab and PANDA at FAIR).
J.L. Taín (IFIC Valencia, Spain) presented the situation of the DESPEC and NCAP calorimeters. The concept in this case is different; they want to take advantage of Total Absorption Technique (TAS). The main requirements of those calorimeters will be the final energy resolution and efficiency. In addition the NCAP calorimeter requires a good timing. These collaborations are considering the use of new crystals. LaCl3(Ce) seems particularly well adapted. Although the characteristics of these calorimeters are different from the ones proposed for R3B and EXL there is a clear interest for common R&D on new scintillator crystal properties and readout possibilities.
J.Gerl (GSI, Germany) presented the “status of the art” on scintillation crystal developments. New materials such as LaCl3 and LaBr3 with very good energy resolution appear as the most promising options. First contacts with the producers (St Gobain) seem to indicate that the crystal treatment is quite expensive and lot of development is still needed before to have a “commercial distribution” of such crystals. J. Gerl proposed the use of “large position sensitive” detectors made of LaBr3 (5x6cm) with double size readout performed with PiN diodes or APD (Hamamatsu). He hast just contacted with an American Company “Radiation Monitoring Devices Inc.” as an alternative to Hamamatsu. This company produces LaBr3 and LaCl3 as well.
I.Durán (Santiago de Compostela, Spain) presented some ideas related with very front end electronics. The proposed “starting solution” will consist on CsI crystals readout with APD’s. Some solutions for the electronic chain were discussed among them the ASIC card developed by the Saclay (CEA, France) group called MATE for the MUST2 detector (see Y. Blumenfeld presentation) and the ASIC electronics PICA chip developed by a company supported by Lund Universtity (see document on the web page). I.Durán pointed out the importance of slow control systems for the big calorimeters allowing to have a continuous control on the T and V.
M. Turrión (IEM-CSIC, Spain) presented the on going activities in the Madrid group that will concentrate on the study of spatial resolution for proton detection using sicntillation arrays and readout with flat PM tubes.
The last presentations were dedicated to the simulation. H. Alvarez (Santiago de Compostela, Spain) presented the activities of the NUSTAR simulation working group and invited the collaborations that have still not jointed this group to do it. As an example he presented the going on simulations for the R3B calorimeter. All these simulations are based on the Geant 4 + Root CERN software. S. España (UCM, Spain) showed some results relative with energy absorption in different crystals with the simulation code PENELOPE.

Discussion


The afternoon was dedicated to the discussion. There are still many open questions that need to be addressed first in the simulation and then with the first prototypes. The effect of the non negligible size of the beam on the target has not been studied. The definition of the first interaction point is still not solved.
The necessary energy resolution needs the use of good intrinsic resolution crystals and high granularity. The use of a large number of crystals will considerably increase the amount of dead layer. In one hand a calorimeter with many different crystal geometries will reduce the dead layer but will increase significantly the manufacturing cost. All these points have to be carefully studied in the on going simulations. The readout proposed in for this calorimeter configuration would consists on APD’s

Action: The USC group will assume this task.
The possibility of using large position sensitive crystals seems very attractive. It is clear that a reduction of the number of crystals will reduce the dead layers. In addition it would keep the electronics in a reasonable price. The readout would be performed either by PIN diodes or APD’s

Action: GSI will perform the first test on this direction
Another direction to explore concerns the use of multianode PM in scintillating arrays.

Action: The IEM-CSIC will work on this topic
The question of coupling the EXL and R3B concepts was mentioned by several participants. The agreement for the moment is to go further with the R&D of the different groups and postpone this decision for our next meeting end of September

Next Meeting



Date of next Working group meeting in Santiago de Compostela (Spain) on 28-30th September 2005 (exact location and time to be confirmed)


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