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Possible solutions for the future CHOD

Mauro Raggi LNFMUV and CHOD

CERN 13/07/2011

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The old CHOD in 2012

The typical PM signal from a hodoscopecounter was 300mV high and 30 ns long.Dynamic range up to 1V (3MIP)

A time resolution better than 200 ps per counter was measured from the data during NA48 data taking.

2 planes x 64 counters per plane 128 ch total

A cost effective and temporary solution for the readout in 2012 is treated in: A LAV FEE based readout for the CHOD @ the synchronization runTDAQ 02/2011

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My view of the future CHOD• My personal constraints

– Increase the number of slab (is a factor 2 enough?)– Reuse the present scintillator material – Possibly reduce CHOD thickness (is 2 cm enough?)– Use a low cost photodetector (Sipm)– Use the LAV FEE+TELL62 readout– Keep the total number of ch<512 using 2thr

• Basic design choice– Maintain 2 planes of scintillators H and V– Maintain the slab structure– Introduce a longitudinal WLS readout

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Single slab design 2x1 cm2 cm

Appropriate length up to 1 meter

Strips of 2x1cm with 2 or 4 x1mm round WLS fibers for all the length read out by 1x4mm2 SipM on one side.The strip should be painted on all sides and glued together to form super strips according to the scaling rate on the CHOD.

1 cm

Hamatsu MPPC (SipM) 1x4mm

2 cm 1 cm Inner radius slab

Outer radius

Middle radius slab

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Detector LayoutH Plane 32x2 cm wide strips 64 mm^2 of Sipm

16x4 cm wide strips 64 mm^2 of Sipm 16x6 cm wide strips 96 mm^2 of Sipm

128 slabs per CHOD planeTotal 256 slabs with 960 fibers 1.5m long

256 read out channels for the whole CHOD~ 1.5 Km of WLS fibers960 mm^2 of SiPM (Hamamatsu or IRST)

2.4m

2.4 m

Each of the 256 slab are optically isolated every 2cmReduce the rate per strip by factor ~3 in the inner part due to smaller size of the stripIncrease the precision of the track positioning to order ~ 1 cm2 in inner partThe size of the readout strip can be easily increased without any intervention on the detector (just read out each 2x2cm cell can reach up to 480 readout channels )SiPM improve light collection by a factor ~3 wrt PMT

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Understanding the rate

According to this picture by Spasimir the rate on the inner slabs should not exceed 400KHz which is safe for both SiPm and TDC

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Fibers radiation hardness• Modern fibers seem to be able to stand dose up to 1Mrad• Even if damaged they recover up 90% of the original LY in

few minutes of no beam• Dose definitions:

– 100rad= 6.24x1012 MeV/Kg which means 6.24x109 MeV/g – 1Mrad = 6.24x1013 MeV/g

• Max number of particle per 1 cm of slab per year– 1MHzx3600s x 24h x 180days =1.5x1013/6.5=2.2x1012 cm

• Energy per particle per fiber:– 1 MeV per cm means 0.1MeV per particle– 1 fiber per cm means geometrical factor of 1/10

• We will have maximum 1.6x1010MeV/g means ~2Krad• We will have more than 2 order of magnitude safety factor

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Cost of the detector material• Fibers cost

– Double cladding 4€ meter means 1.5Km ~ 6K€– Single cladding 2€ meter means 1.5Km ~ 6K€

• Photodetector cost– Sipm 15€ per mm2 1K sipm ~ 15K€

• Low voltage sipm cost to be estimated

Numbers coming from recent order of similar size by KLOE thanks to M. Martini

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Why the LAV FEE for the CHOD• CHOD dynamic range (50mV, 1V)

– The CHOD dynamic range much smaller to the LAV one • FEE board time resolution

– Few hundred of ps time resolution is more than enough with WLS fiber readout

• CHOD charge measurement– A precise charge measurement is not needed for the chod– The LAV FEE can give better than ~10% resolution on charge

• Maximum tolerable rate– The tolerable rate for single ch of LAV readout chain can reach

500KHz limited by HPTDC performance

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LAV FEE working principle

Details in G. Corradi, TDAQ WG dec 2010

Produce a LVDS signal of wdt equivalent to the time the signal is over thresholdClamp the signal Amplify 3 & splitCompare with thr and produce an LVDS

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Online Time slewing correction

THRTHR

LHL LH

TTLTT THR0

Exploiting the presence of a double threshold on the LAV FEE board an online slewing correction is possible for the CHOD: Define TL = leading edge time (ns) for the Lower threshold TH = leading edge time (ns) for the Higher threshold T0 = Time of the event (ns) extrapolated to 0 mV (slewing corrected) LTHR = Lower threshold value in mV HTHR = Higher threshold value in mV

LThr

HThrTH

TL

T0

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Test beam 2010: LAV time resolution

4 mV threshold

Offline slewing correction applied using V(t) ~ ta e-tb

Only TDC used in the correction

More than enough for a WLS based CHOD with 1ns time resolution!

210 ps /√[E10E26/(E10+E26)] (GeV)

D. Di Filippo, P. Massarotti, T. Spadaro LAV WG dec 2010

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LAV FEE charge performanceQ (pC)

ToT (ns)

The charge resolution is very good in a limited range that matches very well CHOD requirement (1-3 MIP range)

%5.2%5%2.9)()(

EELAV

EE

D. Di Filippo, P. Massarotti, T. Spadaro LAV WG dec 2010

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New CHOD readout chainNeed 8 LAV FEE board (32ch in each)1 TEL62 or even TELL14 TDC boards (SCSII connection)1 LAV Wiener crate (9U J1 only)

Each TDC will house half CHOD planeThe TEL62 will house the whole CHOD

4xFEE board

1xTEL62

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new CHOD readout cost estimate

Type of equipment N Cost/1pcsLAV FEE board (32ch in each) 8 3 K€

TDC boards 4 1 K€

LAV Wiener crate 9U 1 7 K€

TEL62 or even TELL1 1 4 K€

Total ~ 40 K€

Plus some cables and infrastructure

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Conclusions• A strip based CHOD design is sketched

– The SIPM readout is cheap and very flexible– The cost of new material is order 20~30K€– No estimate for sipm low voltage yet

• A LAV FEE + TEL62 based readout seems feasible– The cost estimate for 256ch is 40-50K€

• The TEL62 based readout provide an easy way of reproducing pre-trigger algorithms

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Backup slides