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M. Bonesini INFN Milano

A possible design for MICE TOF stations

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OutlineIntroductionConsiderations on environmentTOF stations designSome simulation resultsPMTs testsIdeas for the calibration systemPreliminary cost estimateConclusions

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Aim of TOF stations• TOF0 experiment trigger•TOF0/TOF1 PID on incoming muons•TOF1/TOF2 PID on particle traversing the cooling channel•Requirements:

oSingle detector resolution ~60 ps oHigh rate capabilityoSustain nearby B fringe fields

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TRD SEPT04 Layout

TOF0 TOF1

Ckov1

IronShield

TOF2Ckov2

Cal

ISISBeam

DiffuserProtonAbsorber

IronShield

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…MICETo

F0

Che

renk

ov

Cal

orim

eter

FocusCoils

CouplingCoils

LiquidHydrogenAbsorbers

RFCavities

Tracking Spectrometers

MatchingCoils

Beam Diffuser

Tof1

Tof2

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The environmentThe beamline design puts harder and

harder requests on TOF stations

• Higher and higher particle rates ( now 2.3-2.8 MHz for TOF0, it was ~1 MHz at beginning)• Request for thinner and thinner scintillators (to reduce multiple scattering)• TOF stations in the fringe field of magnets: quadrupoles for TOF0 (B ~ 50-100 gauss), solenoids for TOF1/TOF2 (B~.2 T)

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Summary of Rates (Sept04 from Tom Roberts)

Description LAHET Geant4

MARS

TOF0 2355 2693 2834TOF1 462 529 557

Tracker1 422 482 507Tracker2 284 324 342

TOF2 281 321 338Good μ+ 277 316 333

Values are events per millisecond of Good Target; absorbers empty, no RF.

Good μ+ = TOF0 & TOF1 & Tracker1 & Tracker2 & TOF2 & TOF1(μ+) & TOF2(μ+)

Major changes from before:2 in. total thickness of TOF0 and TOF1 ~20% reduction in Good μ+

~50% larger target acceptance ~10% increase in TOF0 singles, ~1% in Good μ+.

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TOF Detector Layout TOF X/Y planes with PMTs at both ends:TOF0 is placed after Q6.

TOF1 is placed after Q9. TOF2 downstream

Transverse sizes: TOF0,1,2 are all 4848 cm.

Segmentation: All stations are 2 planes arranged

orthogonal to each other. TOF0 has 12 slabs in each plane. NO

OVERLAP (to cope with higher rates) TOF1,2 have 8 slabs per plane. NO

OVERLAPTOF0 environment:

Low field: 100-200 g; High rate: 2.5 MHz.TOF1,2 environment:

High field: 1-2 Kg; Medium rate 0.5 MHz

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Problems for high resolution scintillator based TOF (t < 100 ps) pl dominated by geometrical dimensions

(L/Npe) scint ps (mainly connected with produced

number of ’s fast and scintillator characteristics, such as risetime) choice BC404

PMT dominated by PMT TTS (160 ps for R4998)

• Additional problems in harsh environments:

1. B field (shielding?)2. High incoming particle rates

elec

pe

plPMTsc

t N2

22int

2

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Considerations on scintillator thickness

• Shown time resolution is FWHM vs scintillator thickness L• Green/red lines from BC408; blue line is BC404 (faster) • Data from MEG tests at BTF

Thin solution: 100 ps if all goes right (perfect detector calibration, ...) I will retain thick solution (1” slabs)

Actual choice : 60 ps

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Some simulation studies: TOF0

TRDSize

480x480

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TOF0 X/Y singles projection

With 4 cm width slabs max counter rate seems < 400-500 KHz. R4998 maybe OK with booster

or active divider circuit (studies under way)

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Transit Time for Upstream Tof Planes

•Transit time between Tof0 and Tof1•Quad fields are currently ignored•Pions and muons can be distinguished

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Downstream PID (from Rikard)

good

(No Ckov2)

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Single scintillator counter layout

• BC404 scintillator (compromise between cost and performances: decay time 1.8 ns, att length~ 160 cm, max emission at 408 nm well matched with R4998 max response at 420 nm)•L=480 mm to avoid particles hitting lightguides•W=40 mm to reduce rate with a sensible counter number•T=1” to have good timing resolution

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Mechanics for TOF0

View of X/Y plane: 12 vertical counters , 12 horizontal counters

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TOF0 support structure

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Considerations for TOF0 PMT choice

1. Rate capability (up to some MHz)2. Good timing properties (TTS)3. Sustain magnetic field (we now

assume <50 gauss for TOF0)

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PMT test setup Laser source to simulate MIP signal (about 300 p.e.) :

• fast AVTECH pulser AVO-9A-C (risetime 200 ps, width 0.4-4 ns, repetition rate 1KHz-1MHz) with NDHV310APC Nichia violet laser diode(~400 nm, 60 mW) NEW!!

• fast PLP-10 laser on loan from Hamamatsu ItaliaLaser sync out triggers VME based acquisition (TDC + QADC) // MCA SILENA system Home made solenoid test magnet (B up to 50 gauss, d~20 cm, L~50 cm) see later for details

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Rate capabilities of PMTsTo have a linear signal the mean average anode current (100 A for R4998 ) must not be exceeded -> damage to dynodes ... shorter PMT lifetimeThis gives a theoretical rate capability of:

267 KHZ with R4998BUT !!! Divider can be modified for R4998

(going up to 1.67 MHZ) with booster or active divider

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Solenoid test magnet (B up to 50 gauss)

Test solenoid, PMT inside

Avtech pulser

Laser diode

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Used laser light source (PLP 10)

Light source: Hamamatsu fast laser ( 405 nm, FWHM 60 ps, 250 mW peak power) PLP-10Optical system: x,y,z flexure movement to inject light into a CERAM/OPTEC multimode fiber (spread 14 ps/m) PMT under test

Laser light Signal ~ 300 p.e. to reproduce a MIP as

measured with an OPHIR Laser powermeter

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R4998 PMT rate studies R4998 with modified

divider circuit: booster for last

dynodes

Nominal: up to 1.5 MHz

R 4998 R 5505 Structure Linear Focused Fine Mesh

Stages 10 15 Gain 5.7 106 5 105 B=0

1.8 104 B=1 T Rise Time 0.7 ns 1.5 ns

Transit Time 10 ns 5.6 ns Transit Time

Jitter 0.16 ns 0.35 ns

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Gain in magnetic field for R4998

Y

x

Z50 gauss

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Timimg properties of R4998 in B field

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Rate effects studies for R4998

• done with available R4998 with modified divider from Hamamatsu (booster on last dynodes) • Light signal corresponds to ~ 300 p.e.

1 MHz

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Considerations for TOF1/TOF2 PMT choice1. Rate capability (up to some MHz)2. Good timing properties (TTS)3. Sustain magnetic field ( about 100-200

gauss for TOF0, about .2 T for TOF2)

Tests at Lasa magnet test facility (end July 04, for 15 days) with Pavia MEG group to optimize choice

(M.Bonesini, F.Strati INFN Milano, G.Baccaglioni,F.Broggi, G. Volpini INFN Milano –LASA,

G. Cecchet, A. DeBari, R. Nardo’, R. Rossella INFN Pavia).

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Tests done at LASA Laser source to simulate MIP signal (about 300 p.e.) : fast PLP-10 laser on loan from Hamamatsu ItaliaLaser sync out triggers VME based acquisition (TDC + QADC) 5000 events for each data point : different PMTs (fine-mesh vs mod R4998), different B-field, different inclination vs B field axis (), diff laser rate to simulate incoming particle rates

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Test magnet at LASA (B up to 1.2T)

PMT under test

1. B field up to 1.2 T

2. Free space 12 cm in height

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Fine Mesh Photomultiplier Tubes

Secondary electrons accelerated parallel to the B-field.Gain with no field: 5 x 10 5 – 10 7

With B=1.0 Tesla: 2 x 104 - 2.5 x 10 5

Prompt risetime and good TTSManufactured by Hamamatsu Photonics

R5505 R7761 R5924Tube diameter 1” 1.5” 2 “No. Of stages 15 19 19Q.E.at peak .23 .23 .22Gain (B=0 T) 5.0 x 10 5 1.0 x 10 7 1.0 x 10 7

Gain (B= 1 T) 1.8 x 10 4 1.5 x 10 5

2.0 x 10 5

Risetime (ns) 1.5 2.1 2.5TTS (ns) 0.35 0.35 0.44

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Gain in B field (various orientations)

B (T)

G(T)/G

(0)

2” 1.5” 1”

B(T)

G(B)/G(B=0T)

PMT axis

B

> critical angle

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Pulse height resolution in B field

1” 2”

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Rate effects (as a function of HV)

• rate capability is limited by maximum anode mean current (tipically 0.1mA for a 2” R5924 PMT)• this is the ONLY relevant point, e.g. in B field if gain is lower by a factor F rate capability increases by 1/F• with very high particle rates: try to reduce mean current

HV increase

s

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Rate effect as function of B field

B field increase

s

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Timing studies

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Time resolution

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Calibration of the HARP TOF WallIntrinsic time resolution of scintillators =150 ps

measured with laser system and in lab tests with cosmics

Accurate equalization of time response of the different slabs is achieved with two methodsCosmic muons: Average values of equalization constants Calibration runs every 2-3 months, about

one week Laser: Continuous monitoring of evolution of

equalization constants Calibration runs twice a day, few minutes

during interspill timeM Bonesini – IEEE 2002

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Calibration with cosmicsbefore…

…and after

~220ps

A dedicated trigger setup is installed

Time delays from reference trigger counter to the single slabs are equalized

Time delays of slabs in central wall (ns)M Bonesini – IEEE 2002

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The HARP Laser calibration system

Laser Nd-YAG with passive Q-switch (dye), active/passive mode locking and 10 Hz repetition rateIR emission converted to a second harmonic (=532 nm) by a KD*P SHG crystal

Pulse: width 60 ps energy 6

mJ

Beam splitter:To ultra-fast (30 ps rise/fall) InGaAs MSM photodiode = STARTTo detector slabs through custom-made optical fibre system = STOP

M Bonesini – IEEE 2002

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Comparison of laser with cosmics calibration data

The two calibration methods provide similar accuracy on the equalization constants

The shifts of equalization constants () measured with the two methods are well correlated (within 100ps)

70ps

laserco

smic

s

Shifts of calibration constants from 2001 to 2002 data taking

M Bonesini – IEEE 2002

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Estimate of costsTOF0 PMT assembly R4998 (1600 Euro x 40) 64K Euro scintillators 10K Euro Lightguides machining/supports/… i 5K Euro Electronics mountingsi/patch panels/dividers 5K Euro HV/signal cables 3K Euro 87K EuroTOF1 (or TOF2) PMT assembly 2” fine-mesh (2500 Euro x 35) 87.5KEuro scintillators 10K Euro Lightguides machining/supports/… 5K Euro Electronics mountingsi/patch panel/dividers 5K Euro HV/signal cables 3K Euro 110.5KEuroSist Cal Laser Fast laser + fibers bundle 60K Euro laser diagnostics, electronics 5K Euro

65KEuroSist Cal Cosmici scintillators, support, … 10K Euro

Elettronica front-end QADC,TDC 40K Euro Discriminators 10K Euro NIM electronics 5K Euro Crate VME 8K Euro DAQ modules V1718 (2) 12K Eur 75KEuroHV supply 100 channels CAEN + mainframe 35K Euro

Total 483 KEuro

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Conclusions design for TOF stations well understood only some points to be defined connected with

choice of size of TOF1/TOF2 PMTs (1.5” vs 2”) and divider for TOF0 PMTs (booster vs active divider)

define electronics chain (TDC for high incoming rate): probable choice CAEN V1290

define the high-demanding calibration system (mainly laser based)

test a prototype asap at LNF BTF, together with EMCAL