Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory A vertex detector for the next linear collider Stefania Xella on behalf of the LCFI collaboration: Bristol Univ., Lancaster Univ., Liverpool Univ., Oxford Univ., Rutherford Appleton Laboratory, Queen Mary University London hep.ph.liv.ac.uk/~green/lcfi/home.html

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Next Linear Collider: a challenging environment for a vertex detector Main goal of the next linear collider is to measure PRECISELY the Higgs boson and possibly physics beyond the SM. This requires: High energy and luminosity, which might mean high beam background: Tesla: 50  s = 4 backgr hits/mm 2 at 15 mm radius => fast detector readout Optimal jet/flavour reconstruction due to event topology ee->tt : 6 jets, 2 b and 2 c flavoured ee->HA : 12 jets, 4 b flavoured => very granular, low material budget detector

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Importance of the right design 5 layers, 0.1%X 0 optimal vertex detector design is most important, to reach final physics goal ! PRELIMINARY tagging purity vs efficiency 4 layers, 0.2%X 0

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory LCFI collaboration Linear Collider Flavour Identification collaboration R&D work concentrates on a CCD pixel device : design optimization from physics (see T.Kuhl talk) (RAL PPD/Bristol/Lancaster) CCD development design/test (RAL PPD/E2V/ Liverpool) Readout IC, Driver IC, … (RAL ME/Oxford) Mechanical support (RAL PPD/Oxford)

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Current design (I) Small pixels (20x20  m 2 ) -> precise point resolution thin detector(<0.1%X 0 ) -> less multiple scattering close to the IP (15 mm) -> smaller extrapolation error large polar angle coverage |cos(  )|<0.90 with 5 hits |cos(  )|<0.96 with 3 hits

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Current design (II) 5 layers -> higher resolution -> robust local alignment -> effective gamma conversion fast readout (50  s/layer) -> sustain high integrated background gas cooled, low mass foam cryostat minimal electronics (power + few optical fibres) -> little material at low angles

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Very challenging ! Detector VXD2 VXD3 Future LC CCDs CCD active area Number of pixels Effective no. of layers Inner layer radius (mm) Layer thickness () (2-hit) Imp. param resoln. Readout time 160 ms 216 ms 50/250 (8 ms for NLC) DetectorSLDFuture LC CCDs96120 CCD active area (cm 2 ) n. of pixels (10 6 ) n. of layers35 inner layer radius(mm)2815 layer thickness (%Xo) cos(  ) max0.90 (2 hits)0.96 (3 hits) readout time (1 layer)216 ms50  s (8 ms NLC)

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Column Parallel CCD (CPCCD) Fast readout speed only with Column parallel readout new design! Serial register omitted 50 Mpixels/sec from each column Image section clocked at high frequency Each column has its own ADC/amplifier “Classic CCD” Readout time  N  M/F out N M N Column Parallel CCD Readout time = N/F out

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Readout chip (CPR) CMOS circuit bump bonded to the CCD Each column has amplifier and ADC Correlated double sampling for low noise Sparsification done in the chip Buffer memory and I/O interface

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Ladder end Bump bonding CPCCD- CPR Driver IC provides high frequency (50MHz), low voltage (1.5V pp) clocks 2-phase driven CCD Low inductance connections and layout Small clock and digital feedthrough

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Device simulations ISE-TCAD software used at RAL. Mostly important: To check feasibility of current design Foresee show-stoppers Test new ideas

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Status of R&D program 5 or 6 stage R&D program in collaboration with E2V (former Marconi Applied Technology) company in the UK Test for high speed CCD readout (up to 50MPix/sec) successfully carried out on standard CCD58 device, in serial register Test for radiation damage at different temperatures/RO frequency being carried out CPCCD-1 and CPR-0,1 are (being) produced. Testing during end2002/beg2003 Several options for mechanical support design currently investigated (unsupported/semi-supported)

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory First CPCCD-CPR 2 different charge transfer regions 3 types of output circuitry Independent CPCCD and CPR test possible Designed to work in almost any case! Standard 2-phase implant Metallised gates (high speed) Metallised gates (high speed) Field-enhanced 2-phase implant (high speed) Source followers Source followers Direct 2-stage source followers To pre-amps Readout ASIC Readout ASIC

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory First CPR tests 0.25  m CMOS Charge transfer amplifier (CTA) in each ADC comparator Designed to work up to 50 MHz First CPR produced: small chip (2x6mm), testing flash ADC and voltage amplifiers. Very promising results. Next CPR contains CTA,ADC,FIFO memory in 20  m pitch

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Tests of high speed CCD E2V CCD58 3-phase driven CCD Classical readout (serial register) 12  m 2 pixels 2 outputs 2x10 6 pixels in two sections

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Tests of high speed CCD 55 Fe X-ray spectrum at 50 Mpix/s MIP-like signal (5.9 keV X-rays generate  1620 electrons) Low noise  50 electrons at 50 MHz clocks CCD58 is designed to work with large signals at 10 V pp clocks No performance deterioration down to 5 V pp clocks Still good even at 3 V pp clocks

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory low drive voltage/CTI Clock traces and 55 Fe spectrum for low drive voltages at 50 Mpix/sec Radiation damage effects: beam background expected about 50krad/year (neutron 5x10 9 /cm 2 /year) CTI should improve at fast readout : to be verified CCD58 can be flexibly clocked from 1 to 50 MHZ, so it should be possible to obtain good results for CTE

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Mechanical support R&D Final goal is to design a CCD support structure with Low mass (< 0.1% Xo) Stable shape under repeated temperature cycles down to –100 o C Minimum metastability and hysteresis effects Compatible with bump bonding Robust assembly Able to undergo gentle gas cooling

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Thin ladder options Unsupported CCD : thinned to 50  m and held under tension. Tested experimentally: * sagitta stability found better than 2  m at T>2N, but * large differential contraction at CCD surface causes lateral curling + design is difficult to handle Semi-supported CCD :thinned to 20  m and attached to thin (not rigid) Be support, held under tension. Tested in ANSYS simulation: * CCD surface may become dimpled: under study * may need fine pitched matrix of glue: difficult? => still lots of work to do and ideas to test

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Thin ladder options CCD (20 μm thin) bonded with adhesive pads to 250 μm Be substrate On cooling adhesive contracts more than Be  pulls Si down on to Be surface Layer thickness  0.12% Xo 1 mm diameter adhesive columns inside 2 mm diameter wells 200 μm deep in Be substrate

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Summary The LCFI collaboration R&D program is vast, and very challenging. Its aim is to provide a fast and low material budget CCD based pixel detector to maximize the physics potential of the next linear collider We are only at the first stage of a long R&D program, so stay tuned to hear more !

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Backup slides

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Backgrounds at the nlc

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory CPR-1 FIFO bit flash ADCs Charge Amplifiers Voltage Amplifiers Wire/bump bond pads Bump bond pads In CPR-1: Voltage amplifiers – for source follower outputs from the CPCCD Charge amplifiers – for the direct connections to the CPCCD output nodes Amplifier gain in both cases: 100 mV for 2000 e- signal Noise below 100 e- RMS (simulated) Direct connection and charge amplifier have many advantages: Eliminate source followers in the CCD Reduce power  5 times to  1 mW/channel Programmable decay time constant (baseline restoration) ADC full range:  100 mV, AC coupled, Correlated Double Sampling built-in (CTA does it)

Vertex 2002, Kona, Hawaii S.Xella – Rutherford Appleton Laboratory Semi-supported silicon Carbon fibre: CTE is tunable, layers can have optimal orientation and fibre diameter, difficult to simulate Aerogel support: chemically bonds to Si, aerogel in compression Many other ideas: CVD diamond, vacuum retention, etc … Carbon fibre support Aerogel support