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XI ICFA School on Instrumentation in Elementary Particle Physics Christian Joram / CERN C. XI ICFA School on Instrumentation in Elementary Particle Physics Christian Joram / CERN C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -1

Outline Lecture 1 – Interaction of charged particles Lecture 2 – More interactions: electrons, Outline Lecture 1 – Interaction of charged particles Lecture 2 – More interactions: electrons, photons, neutrons, XI ICFA School on Instrumentation in Elementary Particle Physics neutrinos. Cascades. Lecture 3 – Gaseous Detectors Lecture 4 – Photodetection + organic scintillators • • • Detection of photons (UV, visible, IR) Photoeffect/ photocathodes Detector types (vacuum, solid state, gaseous) Organic scintillators and their readout Applications (scintillating fibres) Lecture 5 – Detector Systems C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -2

Basics of photon detection Purpose: Convert light into detectable electronic signal (we are not Basics of photon detection Purpose: Convert light into detectable electronic signal (we are not covering photographic emulsions!) Principle: Use photoelectric effect to ‘convert’ photons (g) to photoelectrons (pe) • Details depend on the type of the photosensitive material (see below). • Photon detection involves often materials like K, Na, Rb, Cs (alkali metals). XI ICFA School on Instrumentation in Elementary Particle Physics • They have the smallest electronegativity highest tendency to release electrons. C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -3

Basics of photon detection Most photodetectors make use of solid or gaseous photosensitive materials. Basics of photon detection Most photodetectors make use of solid or gaseous photosensitive materials. Photoeffect can also be observed from liquid materials (e. g. liquid noble gases). semiconductor vacuum Solid materials (usually semiconductors) e- Multi-step process: Eg = band gap h (Photonis) However, if the detection method requires extraction of the electron, 2 more steps must be accomplished: 2. energized e’s diffuse through the material, losing part of their energy (~random walk) due to electron-phonon scattering. DE ~ 0. 05 e. V per collision. Free path between 2 collisions lf ~ 2. 5 - 5 nm escape depth le ~ some tens of nm. 3. only e’s reaching the surface with sufficient excess energy escape from it External Photoeffect C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -4 XI ICFA School on Instrumentation in Elementary Particle Physics absorbed g’s impart energy to electrons (e) in the material; If Eg > Eg, electrons are lifted to conduction band. In a Si-photodiode, these electrons can create a photocurrent. Photon detected by Internal Photoeffect. Eg 1. EA = electron affinity

Basics of photon detection Opaque photocathode g Light absorption in photocathode substrate 0. 4 Basics of photon detection Opaque photocathode g Light absorption in photocathode substrate 0. 4 Red light (l 600 nm) a 1. 5 · 105 cm-1 l. A 60 nm Blue light (l 400 nm) a 4· 105 cm-1 l. A 25 nm PC Semitransparent photocathode g Detector window Blue light is stronger absorped than red light ! PC e. C. Joram CERN – PH/DT XI ICFA School on Instrumentation in Elementary Particle Physics e- l. A = 1/a Make semitransparent photocathode just as thick as necessary! Particle Interactions – Detector Design Principles 4 -5

Frequently used photosensitive materials / photocathodes begin of arrow indicates threshold Visible TMAE, Cs. Frequently used photosensitive materials / photocathodes begin of arrow indicates threshold Visible TMAE, Cs. I Ga. As Bialkali K 2 Cs. Sb Multialkali Na. KCs. Sb TEA 250 3. 1 borosilicate glass normal window glass 4. 9 quartz 100 Na. F, Mg. F 2, Li. F, Ca. F 2 12. 3 400 Cut-off limits of window materials C. Joram CERN – PH/DT Si (1100 nm) Infra Red (IR) 2. 24 1. 76 1. 45 E [e. V] 550 700 850 XI ICFA School on Instrumentation in Elementary Particle Physics Ultra Violet (UV) l [nm] Remember : E[e. V] 1239/l[nm] Almost all photosensitive materials are very reactive (alkali metals). Operation only in vacuum or extremely clean gas. Exception: Silicon, Cs. I. Particle Interactions – Detector Design Principles 4 -6

Basics of photon detection Requirements on photodetectors High sensitivity, usually expressed as: or radiant Basics of photon detection Requirements on photodetectors High sensitivity, usually expressed as: or radiant sensitivity S (m. A/W), with XI ICFA School on Instrumentation in Elementary Particle Physics quantum efficiency QE can be >100% (for high energetic photons) ! Good Linearity: Output signal light intensity, over a large dynamic range (critical e. g. in calorimetry (energy measurment). Fast Time response: Signal is produced instantaneously (within ns), low jitter (

(External) QE of typical semitransparent photo-cathodes Photon energy Eg (e. V) 1. 76 3. (External) QE of typical semitransparent photo-cathodes Photon energy Eg (e. V) 1. 76 3. 1 Ga. As. P 1. 13 Ga. As XI ICFA School on Instrumentation in Elementary Particle Physics 12. 3 Ag-O-Cs Cs. Te (solar blind) Bialkali Multialkali (Hamamatsu) Bialkali: Sb. KCs, Sb. Rb. Cs Multialkali: Sb. Na 2 KCs (alkali metals have low work function) C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -8

Latest generation of high performance photocathodes QE Comparison of semitransparent bialkali QE UBA: 43% Latest generation of high performance photocathodes QE Comparison of semitransparent bialkali QE UBA: 43% x 1. 6 Quantum Efficiency [%] 40 30 Example Data for UBA : R 7600 -200 SBA : R 7600 -100 STD : R 7600 Super Bialkali available for a couple of standard tubes up to 5”. SBA: 35% x 1. 3 20 Ultra Bialkali available only for small metal channel dynode tubes XI ICFA School on Instrumentation in Elementary Particle Physics 50 STD: 26% 10 0 200 300 400 500 600 700 Wavelength [nm] C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -9

Family tree of photodetectors Photodetectors Vacuum External photoeffect TMAE MWPC TEA + GEM Cs. Family tree of photodetectors Photodetectors Vacuum External photoeffect TMAE MWPC TEA + GEM Cs. I … External photoeffect Avalanche gain Process Other gain process = Hybrid tubes Dynodes PMT Silicon Continuous dynode Channeltron, MCP Multi-Anode devices Luminescent anodes Solid state Internal photoeffect XI ICFA School on Instrumentation in Elementary Particle Physics Gas PIN-diode APD G-APD (Si. PM) CMOS CCD HPD SMART/Quasar HAPD X-HPD G-APD-HPD Doesn’t exist yet, but was proposed by G. Barbarino et al. , NIM A 594 (2008) 326– 331 C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -10

Photo-multiplier tubes (PMT’s) Basic principle: • Photo-emission from photo-cathode Secondary emission from N dynodes: Photo-multiplier tubes (PMT’s) Basic principle: • Photo-emission from photo-cathode Secondary emission from N dynodes: - dynode gain g 3 -50 (function of - total gain M: XI ICFA School on Instrumentation in Elementary Particle Physics incoming electron energy E); (Hamamatsu) http: //micro. magnet. fsu. edu/ Example: - 10 dynodes with g = 4 - M = 410 106 Very sensitive to magnetic fields, even to earth magnetic field (30 -60 m. T = 0. 3 -0. 6 Gauss). Shielding required (mu-metal). • pe (http: //micro. magnet. fsu. edu) C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -11

Gain fluctuations of PMT’s • Mainly determined by the fluctuations of the number of Gain fluctuations of PMT’s • Mainly determined by the fluctuations of the number of secondary electrons mi emitted from the dynodes; • Standard deviation: • fluctuations dominated by 1 st dynode gain m 1 = d 1 (Photonis) e energy C. Joram CERN – PH/DT 1 pe Pedestal noise Counts SE coefficient d Cu. Be dynodes EA>0 (Photonis) XI ICFA School on Instrumentation in Elementary Particle Physics Poisson distribution: SE coefficient d • Ga. P(Cs) dynodes EA<0 (Photonis) Pulse height 2 pe 3 pe (H. Houtermanns, NIM 112 (1973) 121) Pulse height Particle Interactions – Detector Design Principles 4 -12

(Hamamatsu) Cherenkov rings from 3 Ge. V/c p– through aerogel Multi-anode (Hamamatsu H 7546) (Hamamatsu) Cherenkov rings from 3 Ge. V/c p– through aerogel Multi-anode (Hamamatsu H 7546) • Up to 8 8 channels (2 2 mm 2 each); • Size: 28 mm 2; • Active area 18. 1 mm 2 (41%); • Bialkali PC: QE 25 - 45% @ lmax = 400 nm; • Gain 3 105; • Gain uniformity typ. 1 : 2. 5; • Cross-talk typ. 2% Flat-panel (Hamamatsu H 8500): • 8 x 8 channels (5. 8 x 5. 8 mm 2 each) • Excellent surface coverage (89%) 50 mm (Hamamatsu) (T. Matsumoto et al. , NIMA 521 (2004) 367) C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -13 XI ICFA School on Instrumentation in Elementary Particle Physics Multi-anode and flat-panel PMT’s

 • Photoelectron DV ~ 200 V DV~ 2000 V Gain ~ 106 DV • Photoelectron DV ~ 200 V DV~ 2000 V Gain ~ 106 DV ~ 200 V Dual MCP-OUT Pulse • Anode • MCPs are usually based on glass disks, with lots of aligned pores. The surface of the pores are metal coated. • 50 mm Gain stage and detection are decoupled lots of potential and freedom for MA-PMTs: Anode can be easily segmented in application specific way. Typical secondary yield is 2 For 40: 1 L: D there are typically 10 strikes (210 ~ 103 gain per single plate) Pore sizes range from <10 to 25 mm. Small distances small TTS and good immunity to B-field Dual MCP C. Joram CERN – PH/DT Anode & Pins Ceramic Insulators Particle Interactions – Detector Design Principles Available with up to 1024 (32 x 32) channels (1. 6 x 1. 6 mm 2) photon Window/Faceplate Photocathode 4 -14 XI ICFA School on Instrumentation in Elementary Particle Physics Micro Channel Plate (MCP) based PMTs

Light absorption in Silicon XI ICFA School on Instrumentation in Elementary Particle Physics At Light absorption in Silicon XI ICFA School on Instrumentation in Elementary Particle Physics At long l, temperature effects dominate (http: //pdg. ge. infn. it/~) deg/ccd. html C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -15

Solid-state photon detectors (Si) - Photodiodes: P(I)N type p+ i(n) p layer very thin Solid-state photon detectors (Si) - Photodiodes: P(I)N type p+ i(n) p layer very thin (<1 mm), as visible light is rapidly e absorbed by silicon High QE (80% @ l 700 nm); No gain: cannot be used for single photon detection; n+ h XI ICFA School on Instrumentation in Elementary Particle Physics g Avalanche photodiode: High reverse bias voltage: typ. 100 -200 V due to doping profile, high internal field (>105 V/cm) leads to avalanche multiplication; High gain: typ. 100 -1000; g Rel. high gain fluctuations (excess noise) Avalanche C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles (http: //micro. magnet. fsu. edu) 4 -16

Solid state … Avalanche Photodiode (APD) Reverse structure (short wavelength) Electric field strength XI Solid state … Avalanche Photodiode (APD) Reverse structure (short wavelength) Electric field strength XI ICFA School on Instrumentation in Elementary Particle Physics Traditional ‘Reach-through’ structure (long wavelengths) Used in CMS ECAL; C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -17

Solid-state … Geiger mode Avalanche Photodiode (G-APD) How to obtain higher gain (= single Solid-state … Geiger mode Avalanche Photodiode (G-APD) How to obtain higher gain (= single photon detection) without suffering from excessive noise ? J. Haba, RICH 2007 Photon conversion + avalanche short-circuits the diode. C. Joram CERN – PH/DT XI ICFA School on Instrumentation in Elementary Particle Physics J. Haba, RICH 2007 Operate APD cell in Geiger mode (= full discharge), however with (passive) quenching. Particle Interactions – Detector Design Principles 4 -18

Solid-state … Geiger mode Avalanche Photodiode (G-APD) ID t = RQCD 10 s of Solid-state … Geiger mode Avalanche Photodiode (G-APD) ID t = RQCD 10 s of ns Gain = Q / e = Imax·t / e = (VBIAS-VBD)CD / e G ~ 105 -106 at reasonable bias voltage (<100 V) J. Haba, RICH 2007 Sample of 3 G-APDs C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -19 XI ICFA School on Instrumentation in Elementary Particle Physics Imax~(VBIAS-VBD)/RQ t = RSCD (sub – ns)

Multi pixel G-APD, called G-APD, MPPC, Si. PM, … 1 mm 100 – several Multi pixel G-APD, called G-APD, MPPC, Si. PM, … 1 mm 100 – several 1000 pix / mm 2 Quench resistor XI ICFA School on Instrumentation in Elementary Particle Physics Bias bus O su nly ph rfa pa ot ce rt os is of en si tiv e! GM-APD Sizes up to 5× 5 mm 2 now standard. -Vbias Quench resistor 1 g g g 2 g 20 x 20 pix 3 g GM-APD Q Q 2 Q Musienko @PD 07 Quasi-analog detector allows photon counting with a clearly quantized signal C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -20

You cannot get You cannot get "something for nothing” C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -21 XI ICFA School on Instrumentation in Elementary Particle Physics [email protected] 2007 G-APD show dark noise rate in the O(100 k. Hz – MHz / mm 2) range. The gain is temperature dependent O(5% /°K) The signal linearity is limited The price is (still too) high Hamamatsu catalog • • ~1 th 0 im e m pro te pr ar du pe chn ove ke ce rfo ol m t. E rs rm og en xp are an y a t in ec n t ow ce nd. in Multi pixel G-APD = G-APD, MPPC, Si. PM, …

Hybrid Photon Detectors (HPD’s) Basic principle: • Combination of vacuum photon detectors and solidstate Hybrid Photon Detectors (HPD’s) Basic principle: • Combination of vacuum photon detectors and solidstate technology; Optical window, (semitransparent) photo-cathode; • Electron optics (optional: demagnification) • Charge Gain: achieved in one step by energy dissipation of ke. V pe’s in solid-state detector anode; this results in low gain fluctuations; • Encapsulation of Si-sensor in the tube implies: o compatibility with high vacuum technology (low outgassing, high T° bake-out cycles); o internal (for speed and fine segmentation) or external connectivity to read-out electronics; o e-h Energy loss e. Vth in (thin) ohmic contact WSi = 3. 6 e. V DV = 20 k. V M ~ 5000 heat dissipation issues; F = Fano factor FSi ~ 0. 1 C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -22 XI ICFA School on Instrumentation in Elementary Particle Physics •

Hybrid Photon Detectors (HPD’s) 1 p. e. Pedestal cut 2 p. e. 10 -inch Hybrid Photon Detectors (HPD’s) 1 p. e. Pedestal cut 2 p. e. 10 -inch prototype HPD (CERN) for Air Shower Telescope CLUE. C. Joram CERN – PH/DT pulse height signals of 1 Si pad HVHPD = 26 k. V XI ICFA School on Instrumentation in Elementary Particle Physics 10 -inches (25. 4 cm) 3 p. e. 4 p. e. 5 p. e. pulse height (ADC counts) Photon counting. Continuum due to electron back scattering. Particle Interactions – Detector Design Principles 4 -23

Pixel-HPD’s for LHCb RICH detectors • Cross-focused electron optics • pixel array sensor bump-bonded Pixel-HPD’s for LHCb RICH detectors • Cross-focused electron optics • pixel array sensor bump-bonded to binary electronic chip, developed at CERN • 8192 pixels of 50 × 400 mm. • specially developed high T° bump-bonding; • Flip-chip assembly, tube encapsulation (multialkali PC) performed in industry (VTT, Photonis/DEP) C. Joram CERN – PH/DT T. Gys, NIM A 567 (2006) 176 -179 Pixel-HPD anode During commissioning: illumination of 144 tubes by beamer. In total : 484 tubes. Particle Interactions – Detector Design Principles 4 -24 XI ICFA School on Instrumentation in Elementary Particle Physics 72 mm active 50 mm

Gaseous Photodetectors Principle: (A) Ionize photosensitive molecules, admixed to the counter gas (TMAE, TEA); Gaseous Photodetectors Principle: (A) Ionize photosensitive molecules, admixed to the counter gas (TMAE, TEA); e. g. CH 4 + TEA or (B) release photoelectron from a solid photocathode (Cs. I, bialkali. . . ); TEA, TMAE, Cs. I work only in deep UV region. Bialkali works in visible domain, however requires VERY clean gases. Long term operation in a real detector not yet demonstrated. Thin Cs. I coating on cathode pads Usual issues: How to achieve high gain (105) ? How to control ion feedback and light emisson from avalanche? How to purify gas and keep it clean? How to control aging ? C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -25 XI ICFA School on Instrumentation in Elementary Particle Physics Then use free photoelectron to trigger a Townsend avalanche Gain

Gaseous photodetectors: A few implementations. . . Cherenkov detectors in ALICE, HADES, COMPASS, J-LAB…. Gaseous photodetectors: A few implementations. . . Cherenkov detectors in ALICE, HADES, COMPASS, J-LAB…. Many m 2 of Cs. I photocathodes Built, just starting up: R&D: • Thick GEM structures • Visible PC (bialkali) • Sealed gaseous devices HBD (RICH) of PHENIX. XI ICFA School on Instrumentation in Elementary Particle Physics Proven technology: HV Sealed gaseous photodetector with bialkali PC. (Weizmann Inst. , Israel) photocathode Cs. I on readout pads C. Joram CERN – PH/DT Cs. I on multi-GEM structure Particle Interactions – Detector Design Principles 4 -26

Introduction to Scintillators Energy deposition by an ionizing particle or photon (g) photodetector of Introduction to Scintillators Energy deposition by an ionizing particle or photon (g) photodetector of scintillation light Two categories Inorganic (covered by P. Lecoq) (crystalline structure) Organic (crystals, plastics or liquid solutions) • • • • Up to 70000 photons per Me. V High Z (good for photoeffect Z 5) Large variety of Z and r Undoped and doped ns to ms decay times Expensive Fairly Rad. Hard (100 k. Gy/year) Up to 10000 photons per Me. V Low Z (not good for photoeffect) Low density r~1 g/cm 3 Doped, large choice of emission wavelength ns decay times Relatively inexpensive Medium Rad. Hard (10 k. Gy/year) • E. m. calorimetry (e, g) • Medical imaging C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -27 XI ICFA School on Instrumentation in Elementary Particle Physics scintillator generation transmission detection

Organic scintillation mechanism XI ICFA School on Instrumentation in Elementary Particle Physics The organic Organic scintillation mechanism XI ICFA School on Instrumentation in Elementary Particle Physics The organic scintillation mechanism is based on the pi-electrons (molecular orbitals) of the benzene ring (C 6 H 6). Molecular states (pi orbitals) singlet states S 3 ionization energy 10 -11 s ultra fast S 2 S 1 triplet states nonradiative fluorescence 10 -8 - 10 -9 s fast T 2 T 1 phosphorescence >10 -4 s slow S 0 C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -28

crystals Organic scintillators exist as liquids (solutions) e. g. toluene e. g. p-terphenyl (rarely crystals Organic scintillators exist as liquids (solutions) e. g. toluene e. g. p-terphenyl (rarely used in HEP) solvent plastics (polymerized solutions) (much used in HEP) C. Joram CERN – PH/DT e. g. polyvinlyltoluene XI ICFA School on Instrumentation in Elementary Particle Physics (very rarely used in HEP) + scintillator e. g. Butyl-PBD Particle Interactions – Detector Design Principles 4 -29

Plastic scintillators Often they consist of a solvent + scintillator and a secondary fluor Plastic scintillators Often they consist of a solvent + scintillator and a secondary fluor as wavelength shifter. Solvent wavelength shifter (‘fluor’) Scintillator DE = d. E/dx·Dx fluorescence light Visible (> 400 nm) ~ fast and local energy transfer via non-radiative dipole-dipole interactions (Förster transfer). C. Joram CERN – PH/DT radiative transfer XI ICFA School on Instrumentation in Elementary Particle Physics le ionizing partic UV (~300 nm) A fluor has its absorption and emission spectra shifted. The difference of the two peaks is called Stokes shift Particle Interactions – Detector Design Principles 4 -30

Two / One Dopant scheme solvent + scintillator + wave shifter Förster Radiative B Two / One Dopant scheme solvent + scintillator + wave shifter Förster Radiative B A A solvent + large stokes shift scintillator Förster 0. 0025 molar sol. 0. 025 molar sol. B B C. Joram CERN – PH/DT • Dopants in toluene: large Stokes shift dopants feature a much smaller self-absorption Particle Interactions – Detector Design Principles 4 -31 XI ICFA School on Instrumentation in Elementary Particle Physics Abs. and emission spectra

Scintillators readout Readout has to be adapted to geometry, granularity and emission spectrum of Scintillators readout Readout has to be adapted to geometry, granularity and emission spectrum of scintillator. Geometrical adaptation: “fish tail” (+outer reflector) XI ICFA School on Instrumentation in Elementary Particle Physics • Light guides: transfer by total internal reflection adiabatic • Wavelength shifter (WLS) bars C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -32

 • • Large volume liquid or solid detectors neutron detection underground experiments sampling • • Large volume liquid or solid detectors neutron detection underground experiments sampling calorimeters (HCAL in CMS or ATLAS, etc. ), trigger counters, TOF counters, Fibre tracking (see below) Michigan University: ‘neutron wall’. The flat-sided glass tubes contain liquid scintillator. Scintillating tiles of CMS HCAL. Plastic scintillators in various shapes (Saint Gobain) C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -33 XI ICFA School on Instrumentation in Elementary Particle Physics Most common applications of organic scintillators

Scintillating fibres Working principle of scintillating plastic fibres : cladding (PMMA) n=1. 49 scintillating Scintillating fibres Working principle of scintillating plastic fibres : cladding (PMMA) n=1. 49 scintillating core polystyrene n=1. 59 typically <1 mm cladding (PMMA) n=1. 49 25 mm Double cladding system (developed by CERN RD 7) light transport by total internal reflection q n 1 XI ICFA School on Instrumentation in Elementary Particle Physics typ. 25 mm n 2 (per side) core polystyrene n=1. 59 fluorinated outer cladding n=1. 42 25 mm C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -34

Example: ATLAS ALFA – A fibre tracker (for luminosity measurement) • Technology: Scintillating plastic Example: ATLAS ALFA – A fibre tracker (for luminosity measurement) • Technology: Scintillating plastic fibres, square cross-section, 500 mm overall width, single cladded (10 mm). Type: Kuraray SCSF-78. • Geometry: UV (45°) 1 UV layer 0 50 mm y 50 x Expect: sx = sy ~ 707 / √ 24 mm = 144 mm remember: triangular distribution function C. Joram CERN – PH/DT mm 707 mm 70. 7 mm ultimately: sx = sy ~ 70. 7/ √ 24 mm = 14. 4 mm Particle Interactions – Detector Design Principles 4 -35 XI ICFA School on Instrumentation in Elementary Particle Physics 10 UV layers, staggered by 70. 7 mm

XI ICFA School on Instrumentation in Elementary Particle Physics ATLAS ALFA photo assembly! LHC XI ICFA School on Instrumentation in Elementary Particle Physics ATLAS ALFA photo assembly! LHC ~2 x 1400 fibres C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -36

ATLAS ALFA Beam test CERN SPS November 2009 XI ICFA School on Instrumentation in ATLAS ALFA Beam test CERN SPS November 2009 XI ICFA School on Instrumentation in Elementary Particle Physics plot shows difference of xcoordinates, measured with the two half detectors (5 layers). x 1 - x 2 Expect s. ALFA ~ 32 mm C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -37

XI ICFA School on Instrumentation in Elementary Particle Physics back-up C. Joram CERN – XI ICFA School on Instrumentation in Elementary Particle Physics back-up C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -38

de extra sli wn not sho Dynode configurations of PMT’s • Traditional • Position-sensitive de extra sli wn not sho Dynode configurations of PMT’s • Traditional • Position-sensitive Venetian blind Box (Photonis) (Hamamatsu) Metal-channel (fine-machining techniques) Linear focussing • • • (Photonis) Circular cage (Hamamatsu) “Fast” PMT’s require well-designed input electron optics to limit (e) chromatic and geometric aberrations transit time spread < 200 ps; Compact construction (short distances between dynodes) keeps the overall transit time small (10 – 100 ns). PMT’s are in general very sensitive to magnetic fields, even to earth field (30 -60 m. T). Magnetic shielding required. C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -39 XI ICFA School on Instrumentation in Elementary Particle Physics Mesh

) de extra sli wn not sho X-HPD project (CERN / Photonis) Concept of ) de extra sli wn not sho X-HPD project (CERN / Photonis) Concept of a large spherical tube with central spacial scintillation crystal (X-tal) anode = modern implementation of Philips Smart / Lake Baikal concept. XI ICFA School on Instrumentation in Elementary Particle Physics • Accelerate photoelectron hits scintillator and generates scintillation light: ~ 25 photons/ke. V. • Detect scint light with small external photodetector (e. g. PMT, G-APD). 1 photon = 30 -50 detected photoelectrons. • Radial electric field negligible transit time spread ~100% collection efficiency no magnetic shielding required T ~ 0. 4 QE • Large viewing angle (d. W ~ 3 p) • Possibility of anode segmentation imaging capability (limited!) QE A. Braem et al. , NIM A 602, (2009), 193 -196 • Sensitivity gain through ‘Double-cathode effect’ QEmax ~ 50% observed. C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -40

X-HPD project (CERN / Photonis) X-HPD (PC 120) de extra sli wn not sho X-HPD project (CERN / Photonis) X-HPD (PC 120) de extra sli wn not sho XI ICFA School on Instrumentation in Elementary Particle Physics - 20 k. V - 0 k. V C. Joram CERN – PH/DT Particle Interactions – Detector Design Principles 4 -41