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ILC-inspired TPC for Tlep ?

ILC-inspired TPC for Tlep ?. Philippe Schwemling. Machine relevant parameters. Circumference : 80 km Number of bunches : 4400 ( @ Z peak ) Bunch spacing : 18.2 m (55 ns). CLIC. ILC. Most demanding : lowest energies (Z peak )

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ILC-inspired TPC for Tlep ?

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  1. ILC-inspired TPC for Tlep ? Philippe Schwemling

  2. Machine relevant parameters • Circumference : 80 km • Number of bunches : 4400 (@ Z peak) • Bunchspacing : 18.2 m (55 ns)

  3. CLIC ILC Most demanding : lowestenergies (Z peak) Rates : 16.8 kHZhadronic Z decays (1 every 60 μs avg, or 1 every 1091 BC) 33,6 kHz Bhabhas (1 every 120 μs avg, or 1 every2182 BC)

  4. Whyconsider a TPC atTlep ? • Large (continuous) tracking volume atreasonableprice. • StrongpastexperiencewithTPCs (LEP) • Verylowmaterial budget (typically 0.05 X0 in r, up to 0.25 X0 includingendplates) • Continuoustrackingeases reconstruction of non-pointingtracks : • Physics signatures • PFA • dE/dx measurement (5% resolution)

  5. ILD TPC parameters • R internal : 229 mm • R out : 1808 mm • Z length : 2×2350 mm • Drift gas : Ar CF4(3%) isobutane (2%) • B=4 T • E = 350 V/cm (Arxiv 1006.3220v1) • Otherdata extractedfrom ILC TDR

  6. Gasproperties (Arxiv 1008.5068v2) Dt=50 μm/cm ≈800 μm (Comparable to ILD announced 2-hit r-ϕresol : 2 mm) W=80 μm/ns  drift time = 25μs (B=4 T, E=350 V/cm)

  7. Putting it all together • Average time betweenhadronicevents : 60 μs • Total drift time (electrons): 25 μs  on average, 0.4 hadroniceventdrifting in the TPC • Probability of eventsmixing in z negligible: 2-hit r-z resolutionis 8 mm, or 90 ns drift time, or 1.5 BC • A ILD inspired TPC withMicromegas position measurement looks viable as a TLep detector.

  8. Cooling and power pulsingconsiderations • ILC TPC end-plate power dissipation : 100 W/m2 (with power pulsing, i.e. 1% of the dissipation at 100% duty cycle) • TLep TPC endplate : 2700 W/m2 (not 10 KW/m2, power pulsing gains factor 27 only) • Most of the power comesfrom the back-end, whereprogresscanbeexpected R&D • FE is 5 mW/channel for 10 mm2/channel (500 W/m2 without power pulsing) • However, power pulsingis a source of complication, especiallycommon mode noise.

  9. Is power pulsing possible ? • There willbe a (not power pulsed) Si trackerinside the TPC • There willalsobe a fast (compared to the TPC) calorimeter. If it has to be power pulsed, canalso complementitwith a small non power-pulsed 4 π trigger layer (Si ? Scintillatingfiber ?) • Si tracker and calorimetercanbeused to trigger the TPC readoutelectronics power. • There is a lot of latency to build the trigger decision (60 μs on average) !

  10. Power pulsing in practice HARDROC chip performance studies 2 μs wouldallow a significant power saving. 25 μs isrelativelyuseless, but is the DAC isabsolutelyneeded ? (used to program the internal trigger threshold)

  11. Evaluation of the duty cycle Picture Takenfrom WenxingWang’sthesis Electronics live time : o (1 μs )+ 2 μs duty cycle canbe about 5-10% (on average) TPC endplate power consumptionwouldimmediately go down to 1000 W/m2

  12. Distorsions due to ions Ion drift time is about 1s  ions from 16 800 successive collisions presentatany time in drift volume May bemanageddifferentlyatTlepthanat ILC : gatingsecondary ions easieratTlep because no need for continuousoperation !

  13. Ion back-flow (cont’d) • Primary ions willbe a problem : • Primaryionization due to about 17 k eventspresentat the same time in the TPC • Calculationsexist for ILC, to betransposed to Tlep. • Track distorsion can in principlebecorrectedsince charge distribution isknown • How wellcanthiswork ?  Simulations • Note : ILC momentumresolution performance needdominated by hZ reconstruction. • Is such performance needed for physicsat the Z pole ?

  14. Conclusions • Effect of primary ions • To bequantified • If needed, performance of corrections to bestudied • Some R&D needed to minimize power consumption • Detector performance needed for Z-pole physicsmayberevisited. • Strongexisting detector expertise on TPCsat Saclay (and elsewhere) • A TPC for TLepis an attractive option !

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