Upgrade of the ICARUS T600 Time Projection Chamber

Transcription

1 Upgrade of the ICARUS T600 Time Projection Chamber F. Tortorici 1,2, M. Babicz 3, V. Bellini 1,2, M. Bonesini 4, T. Cervi 5,7, A. Falcone 6, A. Menegolli 5,7, C. Montanari 5, G.L. Raselli 5, M. Rossella 5, C.M. Sutera 2, M. Spanu 5,7, M. Torti 5,7, A. Zani 8 1 Department of Physics and Astronomy, University of Catania, Italy 2 INFN, Sezione di Catania, Italy 3 AGH University of Science and Technology, Krakow, Poland 4 INFN, Sezione di Milano Bicocca, Italy 5 INFN, Sezione di Pavia, Italy 6 University of Texas at Arlington, Arlington, USA 7 University of Pavia, Italy 8 CERN, Geneva, Switzerland 0

2 Overview ICARUS T600 LArTPC technology in a nutshell Generalities on the upgrade of ICARUS PMT tests at CERN Characterization shown: Single Electron Response, gain curve, linearity An example of neutrino event in ICARUS Conclusions 1

3 ICARUS T600 ICARUS (Imaging Cosmic And Rare Underground Signals) is a Liquid Argon Time Projection Chamber (LArTPC), for neutrino physics. Laboratori Nazionali del Gran Sasso (LNGS) Internal dimensions (m): 3.6 (W) x 3.9 (H) x 19.6 (L) 2

4 LArTPC technology in a nutshell 1/3 A passing charged particle (here, a cosmic muon) ionizes the LAr. A fraction of the produced electrons, that depends on the electric field intensity and contaminant concentration, recombines with the ions, giving scintillation light. The remaining part of the electrons drifts and reach three wire planes, where they induce a current in the first two planes, and are collected in the last one. 3

5 LArTPC technology in a nutshell 2/3 Why liquid argon? Noble element: very low reactivity; It can be purified to a large degree; Transparent to its own scintillation light; Relatively cheap w.r.t. similar elements(xenon); It acts as both target and detector; Liquid state is more dense than gas state, so more interactions per time unit; great for neutrino physics, although it requires T=87 K. 4

6 Light per MeV yield (dependences of the order on E of field, photons particle type per and MeV purity) (depends on electric field, particle type and argon Wavelength purity); of emission is 128nm Wavelength of emitted light about Light with 128 two nm. characteristic PMT s are time sensible to constants: the blue region of the visible spectrum, - fast component, so they 6 ns need a WLS; - slow component,1500 ns Light has two characteristic time constants: o LArTPC The Basics: technology in a nutshell 3/3 Argon scintillation light essentials o o Light yield ~ few 10,000 s of photons Argon is highly transparent to its own scintillation light. Fast component, 6ns Slow component, 1500 ns. For more info on LAr scintillation light, see backup slides. J Chem Phys vol 91 (1989) 1469 E Morikawa et al Emission intensities as function of photon energy. 5

7 Typical signal from a PMT Fast light component (from singlet decay) 1 mv 20 ns Slow light from triplet 6

8 An ICARUS PMT: Hamamatsu R5912-MOD Optical fiber Mechanical support Base(designed by Reparto di elettronica di Catania) Power supply (red) and signal (brown) cables 7

9 WA104 Project at CERN: overhauling of the T600 The T600 detector, moved to CERN in December 2014, is being upgraded introducing technology developments while maintaining the already achieved performance: new cold vessels and new purely passive insulation; refurbishing of the cryogenic and purification equipment; better cathode planarity; upgrade of the light collection system; new faster, higher-performance read-out electronics. In addition two items are being discussed, which concern ICARUS and the other experiments involved in the future SBN program at FNAL: the design and construction of a muon tagging system, and the development of fully automatic tools for event reconstruction. 8

10 The light collection system Currently, in ICARUS, light has simply been integrated over all the PMT s. Fine, but light can do more than just the generation of a trigger signal. It can also be used for: The identification of the time of occurrence (T0) of each interaction with high temporal precision; Identification of event topology for fast selection purposes. In order to achieve these goals, there are some requirements to fulfill 9

11 Main requirements 1. High detection coverage, in order to be sensitive to the lowest-expected neutrino energy deposition in the TPC (approximately 100 MeV), also using the light fast-component only; 2. High detection granularity in order to localize the events with sufficient precision to associate unambiguously the collected light to the deposited charge; 3. Fast response time and high time resolution ( 1 ns), to be sensitive to the time of occurrence and to the evolution of each event in the T600 acquisition windows (order of ms). 10

12 Localization resolution Different geometries and cathode coverage area (fraction of the wire plane surface covered by PMT windows) have been tested. The following 90 PMTs per TPC layout (with 5% cathode coverage area) configuration has been chosen. Black dots represent PMT s positions. Longitudinal resolution is better than 0.5 m (effective Q.E. = 5%). A total of 4 modules (so 400 PMT s including 10% of spares) is needed for ICARUS. This geometry addresses main requirements 1 and 2. 11

13 Trigger system The achievement of ~1 ns timing resolution (main requirement 3) implies a PMT timing calibration system to compensate individual channel delays and transit-time drifts. The general approach to the trigger system is the centralization of the basic functionalities into a crate (as during previous ICARUS run at LNGS), hosting Field Programmable Gate Array (FPGA) modules for requesting a coincidence between the beam gate and a majority logic signal from the PMT s. The FPGA s communicate each other via a relatively complex net of internal trigger signals. In the next two slides we will briefly show the trigger system layout, skipping most technicalities. 12

14 16 lines 10 lines... x 2... x 3... x 2... x 3 16 lines 10 lines 16 lines 10 lines... x 2... x 3... x 3 16 lines 10 lines V1730B V1730B 6 V1730B V1730B V1730B V1730B 6 V1730B V1730B 12 Out 12 Out 8 LVDS 5 LVDS... x 11 8 LVDS... x 11 5 LVDS 8 LVDS 5 LVDS 8 LVDS 5 LVDS 4 lines Trig_veto 7 A x 5 A3818 Absolute timing & beam info Fan-out Reset A2795 Trigger system layout 1 TIME_ FPGA Clock Fan-out TTLink_A 12 PMT triggers Fan-out T300_A beam enable A In 6 PMT_ FPGA BNB/NuMI gates Global_Trig_A Global_Trig_B PMT_Trig_A PMT_Trig_B 90 In 192 TPC data opti-links 24 PMT data opti-links TTLink_B TRIGGER CRATE We will see this part in red in the next slide Half chamber 1, 90 PMT s TPC_ FPGA 12 PMT triggers A2795 T300_B RT-controller Fan-out A2795 Event builder(s) 6 Half chamber 2, 90 PMT s DAQ The analog signals from the PMT s are elaborated into logic signals (LVDS standard), that are collected by the PMT_FPGA, which in turn produces a majority PMT trigger (in the red covered region) for each half chamber. In ICARUS there are four half chambers, so the shown layout is duplicated. 13

15 16 lines 10 lines... x 2... x 3... x 2... x 3 16 lines 10 lines 16 lines 10 lines... x 2... x 3... x 3 16 lines 10 lines V1730B V1730B 6 V1730B V1730B V1730B V1730B 6 V1730B V1730B 12 Out 12 Out 8 LVDS 5 LVDS... x 11 8 LVDS... x 11 5 LVDS 8 LVDS 5 LVDS 8 LVDS 5 LVDS 4 lines Trig_veto 7 A x 5 A3818 Beam info Absolute timing & beam info Fan-out Reset A2795 TIME_ FPGA Clock Fan-out TTLink_A 12 PMT triggers Trigger system layout 2 Fan-out T300_A beam enable A In 6 PMT_ FPGA Enable BNB/NuMI gates Global_Trig_A Global_Trig_B PMT_Trig_A PMT_Trig_B 90 In 192 TPC data opti-links 24 PMT data opti-links TPC_ FPGA PMT triggers TTLink_B VETO from tagger TRIGGER CRATE 12 PMT triggers A2795 T300_B RT-controller Fan-out A2795 Event builder(s) 6 DAQ The PMT triggers (see previous slide) are then combined (by the violet TPC_FPGA) with a veto signal from a (cosmic) muon tagger, and an enable signal. The latter comes from the green TIME_FPGA, which checks whether there is beam from the FNAL Booster or from NuMI. 14

16 Characterization of the PMT s Hamamatsu R5912-MOD series (8, 10 dynodes) are rated for cryogenic temperature, as they feature a cathode with platinum under-layer. They are supplied with sand blasted glass windows. The characterization of all 400 such devices focused on these points: gain and linearity; effective Quantum Efficiency (i.e. with Tetra Phenyl Butadiene WLS on window); response uniformity on the photocathode surface; peak-to-valley ratio of the SER distribution. Measurements have been done both at room and at cryogenic temperature. 15

17 Dark room (test at room temperature) Ideasquare CERN Sliding curtain PMT 16

18 Control room (test at room temperature) Ideasquare CERN HV and signal Cables from dark room Power supply crate Optical fibers Pulse signal generator Multichannel analyser LASER 17

19 Cryo tests mechanical support Building CERN 18

20 Building CERN Insertion of the first batch of 10 PMT s in a dedicated dewar for the cryo tests 19

21 Example of fit of a SER spectrum Channel Counts 400 Peak of the Single Electron Response Valley FWHM 500 gaus3 const ± 1.24 gaus2 const 87.4 ± gaus1 sigma ± gaus1 mu ± gaus1 const ± exp tau ± exp const 3885 ± WARM PMT FB V 20

22 Typical example of gain curves of a PMT At room temperature At cryogenic temperature 21

23 Typical measures of the linearity of PMT output (in photoelectrons) Real and ideal amplitudes Real / ideal amplitudes ratio Number of input phe (coincides with the response in the ideal case) 22

24 A beautiful muon neutrino interaction from CNGS run 11689, event 1486 Signals from induction 1 wire plane Entry point of the neutrino Signals from collection wire plane Darker pixel = higher current intensity time e+ e- pair production Wire ID Muon appearing inside the fiducial volume, event trigger tagged as originated from CNGS, and total momentum (3D) direction considerations tell us this is a muon neutrino interaction 23

25 Conclusions In this talk I have shown how 400 Hamamatsu PMT s have been tested at both room and cryogenic temperature, with real experimental results. These PMT s will be used in the configuration of the TPC ICARUS at FNAL. The goal of such accurate calibration and test activity is to have a topological identification of the neutrino events predictably even more clean than the one previously obtained with the configuration of the TPC ICARUS at LNGS 24

26 Backup slides Liquid argon scintillation light trivia 25

27 Mechanisms of Scintillation in LAr Scintillation mechanisms in LAr 1. Self-capture luminescence 1: Self-trapped exciton luminescence + p Ar Ar Ar * Ar Ar * Ar γ Interaction Atomic excitation Self capture Radiative decay Atomic Excitation Self-trapping Radiative decay Phases of the self-capture luminescence in LAr 26

28 Scintillation mechanisms in LAr Mechanisms of Scintillation in LAr Recombination + p Ar + Ar e - e - Ar Ar + Ar Ar * Interaction Ionization Ionization Thermalization of electrons Thermalization of electrons Recombination Ar 2: Recombination luminescence 2. Ar Radiative decay γ Recombination requires electronic cloud about track core Scintillation Yield depends on electric field Recombination step involves an electron cloud around the track core Scintillation -> E-Field dependent Yield depends scintillation on de/dx yield decay Anti-correlation -> de/dx dependent between scintillation charge yield and light -> Charge and light anti-correlation Radiative 27

29 Scintillation mechanisms in LAr Both mechanisms depends on the formation of excimers: Self-capture Self-trapped exciton luminescence + p Ar Ar Ar * Ar Ar * Ar γ Recombination luminescence luminescence + p Ar + Ar e - e - Ar Ar + Ar Ar * 28

30 Scintillation mechanisms in LAr he fate of the excimer states 6 ns Ar Ar Ar * 1500 ns Ar Ar * Ar γ Singlet The singlet state decays into in the argon two atoms argon atoms and and a photon a in photon, in 6ns 6 ns Triplet state decays in 1500 ns There is no agreement in The triplet decays in ~1500 ns literature whether it directly decays Some disagreement to fundamental in the state, or literature via singlet as to whether state. this However, decay proceeds via the singlet, the decay time is much or directly to the ground state longer Either way, time constant much longer than the singlet. 29

31 Impurities reduce yield Quenching of Scintillation L Quenching of Scintillation Light We have seen that the scintillation processes in LAr, anyway, Ar * end in: Ar Ar Ar γ Ar * Ar γ Scintillation process Ar Scin BUT! There is also a dissociative Ar Ar * Competing Excimer Ar Ar * Ar process (competes with Dissociation Process Ar Competing Excimer the former one), and is N N Dissociation Process not radiative: N X N X N X N X * Rate dependent on the d Rate dependent on the density of excimers and density of Rate of these processes depends on concentrations density of of impurity both excimers (green discs) and impurities (blue discs with X), so the purer LAr is, the better! 30

32 LAr is transparent to its own scintillation light Calculations of the excimer state energies of xenon, as a function of nuclear separation J. Chem Phys 52, 5170 (1970) Why are LAr / LXe transparent to their own scintillation light? There are two states at low energy: singlet 1Σu + (red line) and triplet 3Σu + (blue line) Emission at 128 nm Molecular distance about 4A (naïve estimation from density) Typical separation in the liquid phase ground state (~4A, naively from liquid density) So scintillation light is not absorbed! 128 nm photon emission In figure: energy levels as a function of the separation between the atoms of a Ar2 molecule 31

33 Muon passing through the detector top bottom Passing muon top bottom top top side cathode el. δ - not interesting muon direction 3 32

34 10) interesting events passing parallel muons Parallel passing muons run : ev :

35 8) interesting events parallel Parallel muon muon & cascade and e.m. (not go cascade into det.) Run ev 243 p (0.7, 0.72, 0.01) p (0.71, 0.7, 0.03) 32 cm E dep = 490 MeV run : ev :

36 5) interesting events muon interaction Interaraction of a muon in LAr run : ev :

37 6) interesting events interaction before detector Interaction before detector run : ev :

38 11) interesting events stopping muon Stopping muon run : ev : muon decay 18 37

39 4) interesting events muon passing + vx Passing muon, and a neutrino interaction run : ev :

40 I) nu mu CC CC interaction of a muon neutrino muon but not passing + vx run : ev:

41 III) nu NC NC interaction of a neutrino no muons & only vx run : ev :

42 CC Interaction of an electron neutrino MC! II) nu e CC no muon & (only cascade or cascade + vx) p ν = 5202 MeV p e = 4936 MeV p p = 59 MeV p n = 702 MeV p α = 178 MeV type : cluster (not 3d tr) E dep = 2338 MeV d vx = 89 cm (-) range = 115 cm 41 9