CALOCUBE SVILUPPO DI CALORIMETRIA OMOGENEA AD ALTA ACCETTANZA PER ESPERIMENTI DI RAGGI COSMICI NELLO SPAZIO

Transcription

1 CALOCUBE SVILUPPO DI CALORIMETRIA OMOGENEA AD ALTA ACCETTANZA PER ESPERIMENTI DI RAGGI COSMICI NELLO SPAZIO Call nell ambito della CSN5 dell INFN Oscar Adriani, Responsabile Nazionale

2 PHYSICS MOTIVATION And the starting point for the CaloCube proposal.

3 Some of the Cosmic- Ray mysteries 1 particle / m 2 year 1 particle / m 2 second 1 particle / km 2 year High energy nuclei Knee structure around ~ PeV Upper energy of galactic accelerators (?) Energy-dependent composition Structures in the GeV TeV region recently discovered for p and He Composition at the knee may differ substantially from that at TeV Spectral measurements in the knee region up to now are only indirect Ground-based atmospheric shower detectors High uncertainties A direct spectral measurement in the PeV region requires great acceptance (few m 2 sr), good charge measurement and good energy resolution for hadrons (much better than 40%) High energy Electrons+Positrons Currently available measurements show some degree of disagreement in the 100 GeV 1 TeV region Cutoff in the TeV region? Direct measurements require excellent energy resolution (~%), a high e/p rejection power (> 10 5 ) and large acceptance above 1 TeV

4 Our proposal for an optimal CR detector A 3-D, deep, homogeneous and isotropic calorimeter can achieve these design requirements: depth and homogeneity to achieve energy resolution (but please remember that anyway a full containment HCAL is impossible in space!!!!) isotropy (3-D) to accept particles from all directions and increase GF Proposal: a cubic calorimeter made of small cubic sensitive elements can accept events from 5 sides (mechanical support on bottom side) GF * 5 segmentation in every direction gives e/p rejection power by means of topological shower analysis cubic, small (~Molière radius) scintillating crystals for homogeneity gaps between crystals increase GF and can be used for signal readout small degradation of energy resolution must fulfill mass&power budget of a space experiment modularity allows for easy resizing of the detector design depending on the available mass&power

5 The starting point Exercise made on the assumption that the detector s only weight is ~ 1600 kg Mechanical support is not included in the weight estimation The chosen material is CsI(Tl) Density: 4.51 g/cm 3 X 0 : 1.85 cm Moliere radius: 3.5 cm λ I : 37 cm Light yield: ph/mev τ decay : 1.3 µs λ max : 560 nm Simulation and prototype beam tests used to characterize the detector See for example: N. Mori, et al., Homogeneous and isotropic calorimetry for space experiments NIMA (2013) i N N N L of small cube (cm) 3.6* Crystal volume (cm 3 ) 46.7 Gap (cm) 0.3 Mass (Kg) 1683 N.Crystals 8000 Size (cm 3 ) Depth (R.L.) (I.L.) Planar GF (m 2 sr) ** 1.91 (* one Moliere radius) (** GF for only one face)

6 Mechanical idea

7 Electrons Electrons GeV Crystals only RMS~2% Crystals + photodiodes Selection efficiency: ε ~ 36% GF eff ~ 3.4 m 2 sr Non-gaussian tails due to leakages and to energy losses in carbon fiber material (Measured Energy Real Energy) / Real Energy Ionization effect on PD: 1.7%

8 Protons Energy resolution (correction for leakage by looking at the shower starting point) GeV 1 TeV Selection efficiencies: ε 0.1-1TeV ~ 35% ε 1TeV ~ 41% ε 10TeV ~ 47% 32% (Measured Energy Real Energy) / Real Energy 10 TeV 39% 35% (Measured Energy Real Energy) / Real Energy 100 TeV 40% GF 0.1-1TeV eff ~ 3.3 m 2 sr Gf 1TeV eff ~ 3.9 m 2 sr Gf 10TeV eff ~ 4.5 m 2 sr Proton rejection factor with simple topological cuts: up to 10 TeV (Measured Energy Real Energy) / Real Energy (Measured Energy Real Energy) / Real Energy

9 The prototype 14 Layers 9x9 crystals in each layer 126 Crystals in total 126 Photo Diodes 50.4 cm of CsI(Tl) 27 X λi

10 A glance at prototype's TB data SPS H8 Ion Beam: Z/A = 1/2, 12.8 GV/c and 30 GV/c Please note: we can use the data from a precise silicon Z measuring system located in front of the prototype to have an exact identification of the nucleus charge!!!! For deuterium: S/N ~ 14 2 H 4 He

11 Energy deposit for various nuclei Charge is selected with the placedin-front tracking system Preliminary Good Linearity even with the large area PD! Total particle energy (GeV)

12 Charge selected with a silicon tracker located in front (non interacting ions)

13 AN INTENSE R&D AND NEW TECHNOLOGIES ARE NECESSARY TO MOVE FORWARD FROM THIS STARTING POINT!

14 From the idea to the real case A large R&D effort and development of new technologies are necessary to go from the simple idea to a real detector (or better, a real prototype ) The project has a real and strong interest in the CSN2 in view of possible future experiments (GAMMA-400, HERD.) Please keep in mind the importance of the expertise and of the technologies in this field (see DAMPE and GAMMA-400 tracking systems, INFN is receiving money from the space agencies to design and construct the detectors)

15 The CaloCube idea Improve the existing Cubic Calorimeter concept to: 1. Optimize the overall calorimeter performances, in particular the hadronic energy resolution Build up a really compensating calorimeter Cherenkov light Neutron induced signals 2. Optimize the charge measurement Make use of the excellent results from the SPS test Smaller size cubes on the lateral faces Materials to reduce back scattering effect 3. Build up a prototype fully space qualified Mechanics Thermics by developing highly innovative techniques that are one of the core interest of the INFN CSN5

16 Optimization of the overall calorimetric performances (I) Optimize the hadronic energy resolution by means of the dual - or multiple - readout techniques and/or using cubes made by different materials Scintillation light, Cherenkov light, neutron related signals Innovative analysis techniques (software compensation) Possible, due to the very fine granularity Development of innovative light collection and detection systems Optical surface treatments directly on crystals, to collect/convert the UV Cherenkov light Dichroic filters WLS thin layers UV sensitive SiPM and small/large area twin - Photo Diodes New development of front end and readout electronics Huge required dynamic range (>10 7 ) Fast, medium and slow (delayed) signals together New CASIS chip ASIC with integrated ADC

17 The Principle of compensation: f em Cherenkov light detection is a tool to estimate f em in a CsI(Tl) CaloCube! vertical proton 3 TeV

18 And it works! ΔE/E: 35% à 15%

19 It seems that we could disentangle Ch from scintillator in CsI(Tl)! BTF Test beam of the prototype with 500 MeV electrons at the end of September CsI cube wrapped in black, 2 phototubes, both with UV filters (DREAM-like) Signal time profile averaged over many events PT1 PT2 Beam +30 Cherenkov Light!?! Scintillation light Angular dependence is an Great hint Thanks for Cherenkov to DREAM detection groups!!!! -30 PT2 PT1 PT1 PT2

20 CsI(Tl) + Plastic scintillators 24x24x24 (1:1) The number of neutrons N n is correlated to the energy release And delayed signal in plastic scintillator is a good tool to estimate N n!

21 And it (partially) works! ΔE/E: 32% à 26%

22 The technological challenge: life is not as easy as simulation. How technically optimize the Cherenkov or n detection in a difficult environment? Tiny gaps in between the crystals 3-D homogeneity should be maintained Cherenkov signal is tiny wrt scintillation signal Reduced power consumption We are planning detailed R&D activities to obtain the best possible performances WLS or Dichroic UV filters optically deposited directly on the crystals UV sensitive light sensors Dedicated front end chips to handle: Huge required dynamic range (>10 7 ) Fast, medium and slow (delayed) signals together Small power consumption

23 The work inside the call - II Optimization of the charge identifier system - CIS The integration of the charge identifier system inside the calorimeter is a real break through for a space experiment Huge reduction of mass and power Huge reduction of cost Great simplification of the overall structure Thinner size scintillators crystals/cherenkov radiators Pixel structure Multiple readouts in the ion track Back scattering problem to be carefully studied R&D on the front end electronics to reach: large dynamic range excellent linearity low power consumption Positive hints are coming from the SPS beam test

24 The work inside the call - III Space qualification Basic idea: Demonstrate that such a complex device can be built with space qualified technologies Necessary step for a real proposal for space Production of a space qualified medium size prototype (~700 crystals) Composite materials mechanics Thermal aspects Microcooling technologies to cool down sensors and/or electronics Radiation damage issues

25 THE ORGANIZATION

26 The groups involved 1. INFN 1. Firenze 2. Catania/Messina 3. Pavia 4. Pisa 5. Trieste/Udine 2. External institutions 1. IMCB-CNR Napoli à Surface treatments and WLS depositions 2. CNR-IMM-MATIS Catania à Dichroic filters depositions 3. External companies 1. FBK 2. ST Microelectronics

27 Work Packages WP1: System design, software and simulation, prototype construction Responsible: Oscar Adriani - Firenze WP2: Charge identifier system Responsible: Paolo Maestro Pisa WP3: Crystals/radiators and optical treatments Responsible: Sergio Ricciarini Firenze WP4: Photodetectors and electronics Responsible: Valter Bonvicini Trieste WP5: Beam tests Responsible: Sebastiano Albergo Catania WP6: Space qualification Responsible: Guido Castellini - Firenze

28 Conclusions The CaloCube concept is really necessary for the next generation of cosmic ray experiments devoted to the HECR physics Large geometrical acceptance to probe the knee region Excellent electromagnetic energy resolution Excellent hadronic energy resolution with a thin detector (<2λ I ) An intense R&D activity is necessary to go from the idea to a real experiment: I: Optimization of the calorimetric performances II: Optimization of the charge identifier system III: Space qualification This R&D will allow INFN CSN5 to develop new widely appreciated and useful techniques, and INFN CSN2 to profit of these techniques for next generation experiments

29 BACKUP

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33 Mechanical idea

34 The readout sensors and the front-end chip Minimum 2 Photo Diodes are necessary on each crystal to cover the whole huge dynamic range 1 MIPà 10 7 MIPS Large Area Excelitas VTH x 9.2 mm 2 for small signals Small area 0.5 x 0.5 mm 2 for large signals Front-End electronics: a big challenge! The CASIS chip, developed in Italy by INFN-Trieste, is very well suited for this purpose IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 57, NO. 5, OCTOBER channels CSA+CDS Automatic switching btw low and high gain mode 2.8 mw/channel e - noise for 100 pf input capacitance 53 pc maximum input charge

35 MC simulations Fluka-based MC simulation Scintillating crystals Photodiodes Energy deposits in the photodiodes due to ionization are taken into account Carbon fiber support structure (filling the 3mm gap) Isotropic generation on the top surface Results are valid also for other sides Simulated particles: Electrons: 100 GeV 1 TeV Protons: 100 GeV 100 TeV about events per energy value Geometry factor, light collection and quantum efficiency of PD are taken into account Requirements on shower containment (fiducial volume, length of reconstructed track, minimum energy deposit) Nominal GF: (0.78*0.78*π)*5*ε m 2 sr= 9.55*ε m 2 sr

36 A glance at prototype's TB data N B C Please remind that this is a calorimeter!!!! Not a Z measuring device!!!! He Li Be H: Z=1 <ADC>=330 He: Z=2 <ADC>=1300 Li: Z=3 <ADC>=3000 Be: Z=4 <ADC>=5300 B: Z=5 <ADC>=8250 C: Z=6 <ADC>=12000 N Z=7 <ADC>=16000

37 Shower starting point resolution <ΔX> = 1.15 cm

38 Protons Energy estimation Signal / Energy GeV Shower length can be used to reconstruct the correct energy Red points: profile histogram Fitted with logarithmic function Shower Length (cm)

39 ΔE = 17%

40 Proton rejection factor Montecarlo study of proton contamination using CALORIMETER INFORMATIONS ONLY q PARTICLES propagation & detector response simulated with FLUKA q Geometrical cuts for shower containment q Cuts based on longitudinal and lateral development q protons simulated at 1 tev : only 1 survive the cuts LONGITUDINAL electrons protons LatRMS4 LATERAL q q The corresponding electron efficiency is 37% and almost constant with energy above 500gev Mc study of energy dependence of selection efficiency and calo energy distribution of misreconstructed events "#(%,&)/"% λ1 10TeV 1TeV

41 Proton rejection factor E 3 dn/de(gev 2,s -1 ) Protons in acceptance(9,55m 2 sr)/de Electrons in acceptance(9,55m 2 sr)/de Electrons detected/de cal Protons detected as electrons /de cal vela Contamination : 0,5% at 1TeV 2% at 4 TeV An upper limit 90% CL is obtained using a factor X 3,89 E(GeV) = = 0,5 x 10 6 X Electron Eff. ~ 2 x 10 5

42 Response uniformity of the crystals ~14% Uniformity

43 Dual-readout calorimetry with a full-size BGO electromagnetic section N. Akchurin a, F. Bedeschi b, A. Cardini c, R. Carosi b, G. Ciapetti d, R. Ferrari e, S. Franchino f, M. Fraternali f, G. Gaudio e, J. Hauptman g, M. Incagli b, F. Lacava d, L. La Rotonda h, T. Libeiro a,m.livan f, E. Meoni h, D. Pinci d, A. Policicchio h,1, S. Popescu a, F. Scuri b, A. Sill a, W. Vandelli i, T. Venturelli h, C. Voena d, I. Volobouev a, R. Wigmans a, Filter: Dual readout > BGO: scintillation + Cherenkov nm for Cherenkow light >450 nm for Scintillator light Hardware compensation Even better for CsI(Tl) since the scintillation light emission is very slow Fig. 14. Light transmission as a function of wavelength for the two filters used to read out the BGO crystal. The light emission spectrum of the crystal, the spectrum of the Cherenkov light generated in it and the quantum efficiency of the PMTs used to detect this light are shown as well. The vertical scale is absolute for the transmission coefficients and the quantum efficiency, and constitutes arbitrary units for the light spectra. Fig. 5. The time structure of a typical shower signal measured in the BGO em calorimeter equipped with a UV filter. These signals were measured with a sampling oscilloscope, which took a sample every 0.8 ns. The UV BGO signals were used to measure the relative contributions of scintillation light (gate 2) and Cherenkov light (gate 1).

44 f=fem

45 If S/E is significantly different from C/Eà Good energy resolution!

46 Expected number of events Assumptions: 10 years exposure p/e rejection factor ~ 10 5 Depth: 39 X λ Electrons Effective GF (m 2 sr) σ(e)/e E>0.5 TeV E>1 TeV E>2 TeV E>4 TeV 3.4 ~1% Knee Effective GF (m 2 sr) σ(e)/ E Protons and Helium Polygonato Model E>0.1 PeV E>0.5 PeV E>1 PeV E>2 PeV E>4 PeV P He P He P He P He P He ~4.0 35% Heavier Nuclei (2<Z<25) Polygonato Model Effective GF (m 2 sr) σ(e)/ E E>0.1 PeV E>0.5 PeV E>1 PeV E>2 PeV E>4 PeV P He P He P He P He P He ~4.8 32%

47 Response as function of impact point

48 Non interacting ions N B C Please remind that this is a calorimeter!!!! Not a Z measuring device!!!! He Li Be H: Z=1 <ADC>=330 He: Z=2 <ADC>=1300 Li: Z=3 <ADC>=3000 Be: Z=4 <ADC>=5300 B: Z=5 <ADC>=8250 C: Z=6 <ADC>=12000 N Z=7 <ADC>=16000

49 Charge linearity on the single crystal (non interacting ions) Preliminary

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57 Schott UG11 UV Filter