Sensitivity of CNGS muon

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1 Sensitivity of CNGS muon detectors to beam-line misalignments q OUTLINE: Requirements for CNGS muon detectors Beam Loss Monitors as muon detectors Effects of beam-line alignment errors Sensitivity reach to mis-alignments 17 March 22 Francesco Pietropaolo, INFN/Padova 1

2 CNGS beam-line monitoring q CNGS main features: High energy beam (1-3 GeV) optimized for n t appearance No near detector envisaged n m beam normalization performed at LNGS: by experiments (OPERA/ICARUS) with large area muon detectors (n m interactions in up-stream rock) q Requirements for monitors along beam-line Detect mis-alignments of beam-line elements producing significant effects at LNGS: Proton beam wrt Target Horn / Reflector wrt beam axis Monitor beam intensity/stability (relative calibration only) 17 March 22 Francesco Pietropaolo, INFN/Padova 2

3 1 m 1m CNGS: location of beam monitors 7 m 67 m muons profile --> nm profile Francesco Pietropaolo, INFN/Padova 3 SEM foils Hadron profile monitors Proton wrt target Low energy m In principle alignments High energy m optics wrt p-beam alignment 17 March 22

4 Choice of detectors and layout for the muon monitoring stations q Detector: Choice based on results of studies on alignment errors negligible effects on n t rate with alignment errors within predicted accuracy (for all beam line elements) CERN-EP21-37; CERN-SL EA Emphasis on reliability access to muon stations very restricted Muon pit 2 q Layout: Sample muon profile with sufficient accuracy to detect asymmetries # of detectors, spacing, Muon pit Radius (m) 17 March 22 Francesco Pietropaolo, INFN/Padova 4

BLM s as detectors for the muon monitoring stations m beam PRO: robust stable in time large signals (allow distant electronics ª 1 km) good S/N ready to use (with front-end electronics &

5 BLM s as detectors for the muon monitoring stations m beam PRO: robust stable in time large signals (allow distant electronics ª 1 km) good S/N ready to use (with front-end electronics & DAQ) in modules of 36 (18x2 cables) V bias ª 1 kv CONTRA: poor linearity at highest muon flux (under investigation) gas filling (1 bar) N2 17 March 22 Francesco Pietropaolo, INFN/Padova 5

17 March 22 Francesco Pietropaolo, INFN/Padova 6 Fluka standalone Fast parametric simulation After 15 m Fe hadron dump ( 2 GeV range-out filter) After 67 m of molasse ( 5 GeV range-out filter) ª 2 m!

6 17 March 22 Francesco Pietropaolo, INFN/Padova 6 Fluka standalone Fast parametric simulation After 15 m Fe hadron dump ( 2 GeV range-out filter) After 67 m of molasse ( 5 GeV range-out filter) ª 2 m! r (m) r (m) p ±, p ±, K ±, m ± (1 13 pot cm 2 ) un-collided proton peak m + (1 13 pot cm 2 ) -1 x 1 1 x m + (1 13 pot cm 2 ) -1 Hadron monitor 7 x first muon pit second muon pit BLM s characteristics: matching muon beam intensity and pit layout

7 17 March 22 Francesco Pietropaolo, INFN/Padova 7 Clear loss around Horn focused momenta Loss -2.8 ±.2 % First muon pit very sensitive to Horn focused particles Average displ. = 19.1 ±.5 cm Second muon pit sensitive to much higher energies Average displ. = -3.5 ± 1.2 cm E (GeV) r (m) r (m) n t CC evts (GeV kt year) sin 2 2q = Dm 2 = ev 2 x m + (1 13 pot cm 2 ) -1 n t evts at LNGS x first muon pit x 1 5 second muon pit 3.5 m + (1 13 pot cm 2 ) -1 Mis-aligned case Aligned case Example 1: 6 mm horn lateral displacement (expected accuracy ª.1 mm!!) Effects of alignment errors

8 17 March 22 Francesco Pietropaolo, INFN/Padova n t CC evts (GeV kt year) x m + (1 13 pot cm 2 ) n t evts at LNGS x first muon pit second muon pit m + (1 13 pot cm 2 ) x 1 5 Example 2: 1 mm p-beam lateral displacement (expected accuracy ª.1 mm!!) Effects of alignment errors

9 Overall effects of CNGS beam-line misalignments n t CC interact. loss (%) 1 st muon chamber centroid displ. (cm) 2 nd muon chamber centroid displ. (cm) Proton beam lateral displacements (alignment accuracy ª.1mm).5 mm 1. mm Proton beam angular displacements (alignment accuracy ª.1mr).5 mr 1. mr Small effects at LNGS Measurable along beam-line Horn lateral displacements (alignment accuracy ª.1mm) 3 mm 6 mm Reflector lateral displacements (alignment accuracy ª.1mm) 1 mm 3 mm >>>> Statistical accuracy of the MC simulation <<<< Muon monitors (complemented by SEM s at target) are sufficient to disentangle source of misalignment 17 March 22 Francesco Pietropaolo, INFN/Padova 9

10 Study of the layout of BLM s in the muon monitoring stations Working hypotheses: 18 BLM s per pit s meas 3% / full scale (mainly relative calibr.) max signal adjusted at full scale good linearity over full signal range Arrangements (17 BLM s): Centered on beam axis Left/Right symmetric Orthogonal Polar Estimator: Weighted sum of (L-R) differences Depends on s meas, DS, number of BLM s No need for absolute calibration! DS Goal: best arrangement best spacing (DS) minimal number of BLM s 17 March 22 Francesco Pietropaolo, INFN/Padova 1

11 Detecting asymmetries in muon profiles Estimators of projected displacements: depend on left/right differences along given direction Dx = Â x i W i,j / Â W i,j = DS Â i cosq j [W i,j -W -i,j ] / Â W i,j i,j i,j i>,j i,j y i q j x Dy = Â y i W i,j / Â W i,j = DS Â i sinq j [W i,j -W -i,j ] / Â W i,j i,j i,j i>,j (W ij = muon flux measurement in each detector) i,j DS Errors: s ª s DS 2 (i cosq x meas Â j )2 / Â W i,j i>,j i,j Estimator of sensitivity: Dr = Dx 2 +Dy 2 Dq = inv sin( Dy Dr ) s ª s DS 2 (i sinq y meas Â j )2 / Â W i,j i>,j i,j s q ª s r Dr = s x 2 + s y 2 Dr 17 March 22 Francesco Pietropaolo, INFN/Padova 11

12 Simulations q Extensive simulation of possible misalignments Proton beam wrt target - horn/reflector wrt beam-axis Focus on small displacements (sensitivity) Several displacement directions (x,y) q Wide variety of arrangements of 17 BLM s tested Orthogonal configuration 4 BML s per row Spacing for 1cm to 5cm Polar configuration 8 BLM s per circle Spacing from 2cm to 1cm Non-uniform spacing also tested Grouping BLM s where muon profiles vary rapidly x q Double BLM s density (33 per muon station) also tested muon pit x-slice (m) 17 March 22 Francesco Pietropaolo, INFN/Padova 12

13 17 March 22 Francesco Pietropaolo, INFN/Padova cm Dr (cm) 8 Estimator Dr approaches muon profile average displacement when the full distribution is sampled Best sensitivity for minimum s r /Dr 1 Sensitivity to beam-line mis-alignments (I)

14 17 March 22 Francesco Pietropaolo, INFN/Padova Relative error cm Best monitor spacing, DS, depends on muon profile width Polar/orthogonal configurations equivalent sensitivity Sensitivity to beam-line mis-alignments (II)

15 Sensitivity to beam-line mis-alignments (III) 1 st muon chamber (max spanned radius = 8 cm) Horn lateral displacements 3 mm 6 mm % 8% 2 nd muon chamber (max spanned radius =12 cm) Proton beam lateral displacements.5 mm 1. mm s meas = 3% / full scale n t CC interact. Loss (%) Centroid profile displ. (cm) Relative error (%) 16 BLM s 32 BLM s 18% 1% 6% 3% 7% 4% wide variety of configurations (uniform/non-uniform spacing) give comparable sensitivity 16+1 BLM s allow detecting displ. with negligible effect at LNGS (assuming s meas = 3% / full scale) 32+1 BLM --> factor 2.5 better (more detailed description of muon profiles) 1 motorized BML for x-y scanning and cross-calibration 17 March 22 Francesco Pietropaolo, INFN/Padova 15

16 Summary Misalignments of the beam-line elements -within project values- will not affect n t event rate at Gran Sasso Muon monitoring arrays (based on BLM s) - located after the CNGS dump - should provide reliable information to control beam intensity and misalignments Optimization of BLM s design and layout is underway to match CNGS highest muon flux 17 March 22 Francesco Pietropaolo, INFN/Padova 16

17 BLM characteristics q Ionization camber Diameter 9.2cm Length 19cm Volume 1liter Filling N 2 (99.9%) Pressure 1bar Ionization energy 27eV Sensitivity C/Gy Efficiency pairs/part. Bias Voltage 8V (5-12V) Rise-time 3ns Dynamics > 1 6 q Electronics and DAQ Acquisition mode integration ADC full scale 1V Resolution 12bit Integrator capac. min 5pF max 5mF DAQ unit 36(+4) channels 1 CPU+Timinig Signal cables 18 channels Cable length max 15m Acqusition time 3ms (36ch.) q Performance (Cable <5m; C min = 1nF) Radiation resist. > 1 6 Gy q Calibration Single source (137Cs - 3mCi) --> few % cross-calibration & time stability Drift 1bit/s Noise 3bit Sens part./bit Full scale part. 17 March 22 Francesco Pietropaolo, INFN/Padova 17

The CNGS neutrino beam

10th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD06) 1-5 October 2006 Siena, Italy ν The CNGS neutrino beam G. Sirri INFN Bologna CNGS (CERN Neutrinos to Gran Sasso) The project