Possible solutions for the future CHOD

1. Possible solutions for the future CHOD Mauro Raggi LNF MUV and CHOD CERN 13/07/2011

2. The old CHOD in 2012 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 The typical PM signal from a hodoscope counter was 300mV high and 30 ns long. Dynamic range up to 1V (3MIP) A cost effective and temporary solution for the readout in 2012 is treated in: A LAV FEE based readout for the CHOD @ the synchronization run TDAQ 02/2011

3. 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

4. Single slab design 2x1 cm 2 cm 2 cm 1 cm Inner radius slab 1 cm Middle radius slab Outer radius Hamatsu MPPC (SipM) 1x4mm Appropriate length up to 1 meter Strips of 2x1cm with 2 or 4 x1mm round WLS fibers for all the length read out by 1x4mm2SipM 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.

5. Detector Layout H 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 plane Total 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 2cm Reduce the rate per strip by factor ~3 in the inner part due to smaller size of the strip Increase the precision of the track positioning to order ~ 1 cm2in inner part The 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

6. 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

7. 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 6.24x109MeV/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

8. 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 mm21K sipm~ 15K€ • Low voltage sipm cost to be estimated Numbers coming from recent order of similar size by KLOE thanks to M. Martini

9. 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

10. LAV FEE working principle Produce a LVDS signal of wdt equivalent to the time the signal is over threshold Clamp the signal Amplify 3 & splitCompare with thr and produce an LVDS Details in G. Corradi, TDAQ WG dec 2010

11. Online Time slewing correction 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 T0 LThr TL TH HThr

12. Test beam 2010: LAV time resolution Offline slewing correction applied using V(t) ~ ta e-tbOnly TDC used in the correction 4 mV threshold 210 ps /√[E10E26/(E10+E26)] (GeV) More than enough for a WLS based CHOD with 1ns time resolution! D. Di Filippo, P. Massarotti, T. Spadaro LAV WG dec 2010

13. Q (pC) ToT (ns) LAV FEE charge performance The charge resolution is very good in a limited range that matches very well CHOD requirement (1-3 MIP range) D. Di Filippo, P. Massarotti, T. Spadaro LAV WG dec 2010

14. New CHOD readout chain Need 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 plane The TEL62 will house the whole CHOD 4xFEE board 1xTEL62

15. new CHOD readout cost estimate Plus some cables and infrastructure

16. 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

17. Backup slides