Crystals !? R3B/EXL meeting Milan Oct-06

Crystal growing factories Quality and price on 20(23)*20(23)*110 mm 3 detector light output uniformity* price AMCRYS Ltd, Kharkov, Ukraine< 2% measured 3.72 US$/cm 3 St. Gobain Crystals< 5% guaranteed, < 2% measured US$/cm 3 Shanghai SICCAS High Tech. Coorperation< 2% measured 4.32 US$/cm 3 SCIONIX 2.8% measured IMP Lanzhou *) after identical surface treatment and wrapping?

Results CsI(Tl)+Teflon+XP5300B+ 137 Cs RS=5,5%±0,2 except for crystal 22x22x220: RS~7% Global Resolution is quite constant along the Crystal Variation from 14% to 38% of collected light along the Crystal Resolution FWHM Collected light for 137Cs peak VS position of impact

Photon test facilities Lund, MAX-lab., tagged photon beam Energy 14 – 220 MeV, beam energy resolution 0.4 MeV at 14 MeV (from tagger system) We will ask for ~8 MeV. How do we improve the energy tagging – shift of the two tagger planes or insert Si detectors to measure electon energy? VdG p + 11 B  gamma Etc (Madrid?) Mainz, tagged photons -- only high energies! Others ?? Source tests up to 3 MeV

The CsI(Tl) calorimeter as photon detector: The detectors must serve as - EMC - multiplicity - Σ (E) - Spectroscopic gamma detector (4% energy resolution at 10 MeV) A lot of homogeneity tests have been performed. They all point in the same direction.  We have to optimize the surface treatment, the light-guide geometry etc, to the level where it is still possible to ask for it from the producers (or find facilities within CWG). We must use APD (or PMT) readout for E γ < 1MeV The LU/JINR group is trying to establish a high energy photon test station. Facilities in Lund (MAX-lab and Dubna are considered but also other possibilities [VdG with (p,  ) exchange reactions] are investigated (Madrid?). For low energy  irradiation a combination of various radioactive sources seems relevant.

R3B/EXL meeting Milan Oct crystals (approx. 1 x 2 x 17 cm 3 ) APDs S (Hamamatsu) mechanical structure  IPNO concept temperature and voltage stabilisation full simulation electronics  Saclay digitizers ?? DAQ  VME/MBS Beam-test of the Barrel concept with a realistic prototype: USC Barrel Prototype

Crystal type-2 Bi-frustrum shaped Waiting for an agreement with StGobain and IMP- Lanzhou(China) --> Price drop! Exit face fits to LAAPD S under negotiation First prototypes done at Lanzhou (China Further tests through prototype Good results are only achieved when there is a perfect matching between the crystal exit surface and the APD entrance area Type 2 View of the Barrel average dimensions 3x1x13 cm

Possible Calorimeter Design Prototype In 2008, construction of a prototype of 18 Xtals [CsI(Tl)] with 9 square PMT Simulation and Tests of the prototype with different thickness of material in between the crystals depending on mechanical and physics considerations.

Crystal type-2 Bi-frustrum shaped Waiting for an agreement with StGobain and IMP- Lanzhou(China) --> Price drop! Exit face fits to LAAPD S under negotiation First prototypes done at Lanzhou (China Further tests through prototype Good results are only achieved when there is a perfect matching between the crystal exit surface and the APD entrance area Type 2 View of the Barrel average dimensions 3x1x13 cm

Dear Prof. Jakobsson, As we know (also confirmed by Prof. Gerl) LaBr3(Ce) is happend to be the best choice of crystal for building our calorimeters ---considering the experiments to be performed using these calorimeters. For R3B: <30 MeV gamma, < 300 MeV proton, huge Doppler effects EXL: <30 MeV gamma, < 100 MeV proton, huge Doppler effects DESPEC: <10 MeV gamma And the challenges are: 1. Required effective granularity > 10, Energy resolution 1.3 MeV. 3. Reasonable cost. We, from India trying to address the above 3 challenges assuming LaBr3(Ce)--which is the best choice, as the crystal for our all the 3 calorimeters. Now to address the above issues, we're making an MoU with Saint-Gobain Crystals --a joint venture of Indian research institutes/industries and Saint-Gobain Crystals, BANGALORE. In this joint venture, R & D related to "LaBr3(Ce) yield improvement" (which is required to bring down the cost of the final product--- apart from detector fabrication expenses) & others (like required "timing resolution" which depends on Ce concentration) will be jointly addressed by Indian research institutes and Saint-Gobain at their Bangalore facility (a medium capacity LaBr3 growth facility will be established in Bangalore by India-Saint Gobain joint venture with cost sharing basis. Saint-Gobain does not have any LaBr3 growth facility at Bangalore presently. They grow only CdWO4 here). The research output will be fed to their France unit for mass production. The grown cyrstals will then be brought to Bangalore for finishing, integration...making detector etc. where Indian industries will participate. A summary on the proposal from U.K. Lal, BARC, India (text directly from )

Here all the Indian services and R & D efforts provided to Saint-Gobain will be free of cost --- will not be taken into account to estimate the final cost of the product.Hence the final cost will be very low ---which is NOT possible for Saint-Gobain without utilising Bangalore facility and Indian expertise and services ! And finally using those detectors all the THREE calorimeters will be builtat BARC which has got an excellent design and manufacture centre comaparable to any national lab in the world. Now, coming to design studies of this crystal --we've just started workingwith LITRANI -- according to Prof. Gerl's suggestion since last Oct./Nov.about which I wrote you yesterday also. We want to study all the test experiments for LaBr3(Ce) (light collection with PMT/APD/... collection surface geometry.... what the Spanish group is doing for CsI(Tl). This is just our beginning. We've NOT attended any CWG-meeting held so far. Hopefully, in the next meeting I'll present our studies for this crystal (supposed to be the actual crystal for our calorimeters !) This is our message from Trombay group from India (to the CWG-Lundmeeting), for solving the challenges with the right crystal. Sincerely, Dr.U.K. Pal, NPD, BARC

Conclusions (Milano, Oct. 06) 1.Collected light through long crystals is not constant. Tests with non collimated 137 Cs source give resolutions greater that 15%. 2.The choice of VM2000 seems obvious 3.With XP1912, it seems difficult to have a resolution better than 9%-10% at 662keV on long crystals because: a.Area covered by PMT is only 36% with 22x22 output face b.Intrinsic resolution of crystal is quite high (~4/5%) c.Photocathode is not green extended bialkaly 4.Resolution obtained with PMT XP1912 and APD are quite comparable until 3.25MeV 5.No work has been done on surface quality (polished/rough) 6.Use of XP1452 seems promising 7.Tests on LaCl 3 crystal

”New conclusions” 1.Collected light through long crystals is not constant. Tests with non collimated 137 Cs source give resolutions greater that 15%. Can be handled – but to which extent by producer? 2.The choice of VM2000 seems obvious. Confirmed! 3.With XP1912, it seems difficult to have a resolution better than 9%-10% at 662keV on long crystals because: a.Area covered by PMT is only 36% with 22x22 output face b.Intrinsic resolution of crystal is quite high (~4/5%) <2% c.Photocathode is not green extended bialkaly ? Can be improved – also with APD (+PD?) 4.Resolution obtained with PMT XP1912 and APD are quite comparable until 3.25MeV  APD (stabilisation!) 5.No work has been done on surface quality (polished/rough) A lot of this kind of work has been done now 6. Use of XP1452 seems promising or  APD? 7. Tests on LaCl 3 crystal Promising but cost is high and development time long