1、P. Colas - TPC R&D,1,KEK, May 9th, 2007,D-R&D-2: TPC R&D,R&D for TPC applicationsA TPC for the ILC,KEK, May 9th, 2007,P. Colas - TPC R&D,2,ILC International Linear Collider,3 designs out of 4 chose a TPC as a main tracker,The R&D is carried out worldwide by the LC-TPC collaboration,KEK, May 9th, 200
2、7,P. Colas - TPC R&D,3,TPC Time Projection Chamber,E,Ionizing particle,Electrons separate from ions,The electrons drift under the E field,x-y coordinates given by the pads z coordinate given by the time,B,t,x,y,The magnetic field reduces electron diffusion,KEK, May 9th, 2007,P. Colas - TPC R&D,4,Mic
3、romegas and GEM,GEM: Two copper perforated foils separated by an insulator (50 mm)Multiplication takes place in the holes.Usually used in 2 or 3 stages, even 4,Micromegas : a micromesh supported by 50-100 mm - high insulating pillars. Multiplication takes place between the anode and the mesh.One sta
4、ge,200 mm,KEK, May 9th, 2007,P. Colas - TPC R&D,5,Outline,The teamCollaborative activities since 2005AchievementsProjects,KEK, May 9th, 2007,P. Colas - TPC R&D,6,The team,FRANCECEA/Dapnia Saclay(D. Burke)M. ChefdevilleP. ColasA. GiganonI. GiomatarisM. RiallotF. SneS. TurnbullCNRS/IN2P3 OrsayV. Lepel
5、tier (LAL)Ph. Rosier (IPN)T. Zerguerras (IPN),JAPANKEK/IPNSK. FujiiM. KobayashiH. KuroiwaT. MatsudaR. YonamineSagaA. Aoza(H. Fujishima)T. HigashiA. IshikawaA. SugiyamaH. Tsuji,Kinki U.Y. KatoT. YazuK. HiramatsuHiroshima U.T. TakahashiTokyo TUATM. Bitou(M. Habu)(K. Nakamura)O. NitohH. OhtaK. SakaiKog
6、akuinT. Watanabe,KEK, May 9th, 2007,P. Colas - TPC R&D,7,Collaborative activities,(pre-)HistoryIn Japan : CDC group, legacy of Tristan and LEP/SLC, back to the 1990s, worked on a Central Drift ChamberIn Europe and America: in the the early 2000s, started R&D on MPGD TPCs. In 2002, M. Ronan, M. Dixit
7、 and P.C visited KEK and advertised TPC. In 2003-2004, R. Settles (MPI Munich) initiated a collaboration to test the 3 technologies : wires, GEM and Micromegas.,KEK, May 9th, 2007,P. Colas - TPC R&D,8,Collaborative activities,In 2004 in Paris, we (Orsay-Saclay) decided to join and to bring a Microme
8、gas endplate, adapted to the MPI field cageUse the PCMAG magnet(s) and the p2 4 GeV pion beam at KEK PS, the trigger setup, and the ALEPH electronicsFrom pictures and mail exchanges, we made a 384-pad endplate and installed it at KEK in June,KEK, May 9th, 2007,P. Colas - TPC R&D,9,In June 2005, we i
9、nstalled commissioned and took beam data,From France:Paul ColasArnaud GiganonVincent LepeltierThomas Zerguerras,KEK, May 9th, 2007,P. Colas - TPC R&D,10,Collaborative activities,As the beam was available only until december, we decided to organise another data taking to test a new technique to sprea
10、d the charge: the resistive foil technique (M. Dixit et al., Carleton U.)A second endplate was built in Saclay, with a resistive coating on the anode, and both the MPI and Carleton TPCs were run simultaneously in the same beam, push-pulling in the magnet.,KEK, May 9th, 2007,P. Colas - TPC R&D,11,- M
11、icromegas 10 x 10 cm2- Drift distance: 16 cm- 126 pads, 2 x 6 mm2 each in 7 rows ALEPH preamps + 200 MHz FADCs,Micromegas 10 x 10 cm2 Drift distance: 25 cm - 384 pads, 2.3 x 6.3 mm2 each in 16 rows ALEPH preamps + 11 MHz AlephTime Projection Digitizers,Carleton-Saclay TPC,MP-TPC,Charge dispersion re
12、adout endplates,Micromegas,Beam tests in October 2005 at KEK,KEK, May 9th, 2007,P. Colas - TPC R&D,12,Spreading of charge due to foil can be seen across six pads,KEK, May 9th, 2007,P. Colas - TPC R&D,13,France-Japan meeting(s) in Paris in September 2006, followed by a 3-day endplate meeting with a l
13、arge Japanese attendance (K. Fujii, Y. Kato, H. Kuroiwa, T. Matsuda, A. Sugiyama)http:/www-dapnia.cea.fr/Spp/Meetings/EndPlate/,For the first time, a french attendance at the japanese MPGD meeting in Saga, in January 2007 (D. Atti, P. Colas),Participation of K. Fujii in a TPC analysis “Jamboree” in
14、Aix-la-Chapelle, March 2007,KEK, May 9th, 2007,P. Colas - TPC R&D,14,Gasbox for studying gas gain fluctuations from the resolution on the 55Fe 5.9 keV line,Blueprints drawn in Saclay. Realisation at KEK.,2 of these gasboxes built in Saclay, for gas+pixel and aging studies,Saclay,KEK,KEK, May 9th, 20
15、07,P. Colas - TPC R&D,15,The CF4 “saga”,We tried to take data with Ar CF4The detector was very unstable, very different from what we had in Saclay, with afterpulses.We suspected Japanese CF4 to be different from European CF4After a complicated exchange of bottles and careful gas analyses, the two ga
16、ses were shown to be the sameThe difference was traced to the presence of impurities in the gas system in Saclay, quenching UVsAn admixture of 2% isobutane was found to be enough to stop the UVs and stabilise the operation.This gas Ar CF4 isobutane (fast, low diffusion) is likely to be used by T2K a
17、nd is favored for the ILC. It is being tested in KEK.,KEK, May 9th, 2007,P. Colas - TPC R&D,16,Analysis of theJune test beam,April-May 2006 : data analysis with 2 independent methods / programs,KEK, May 9th, 2007,P. Colas - TPC R&D,17,Achievements,Cross-check of gas purity and MC simulation,Using a
18、beam at 45 deg. Look at time distribution on one pad. Max time gives drift time over 26.08+-0.02 cm (add trig. delay),1 cm scint.,cathode,Vdrift (Ar+5%iso, E=220V/cm) = 4.181 +- 0.034 cm/msIn agreement with Magboltz : 4.173 +- 0.016,Drift velocity measurement,KEK, May 9th, 2007,P. Colas - TPC R&D,18
19、,Measurement of the diffusion coefficient at B=0, 0.5 and 1T,in m/cm,2 methods: global likelihood fit of the track width to all pad charges (shown here), or width of the PRF (slope at large distance is unbiased),Good agreement between the two methods and good agreement with Magboltz.,KEK, May 9th, 2
20、007,P. Colas - TPC R&D,19,Understanding the basic limitations of the resolution,Triggered by discussions on the data, the role of the ionization statistics, gas gain fluctuations and finite pad width were studied in detail (K. Fujii, M. Kobayashi)Asymptotically, s2=s02+(DT2/Neff) zWhy is Neff much s
21、maller than Ntot ?,Achievements,KEK, May 9th, 2007,P. Colas - TPC R&D,20,Study of the resolution (theory),At large drift distance, transverse diffusion dominates: resol CDz/NeffNeff different from Ntot because of Ionisation fluctuations 1/Gain fluctuations: x /2At small distance, hodoscope effect: n
22、ot enough charge spreading by diffusion to encompass more than 1 pad,Ex: for 60 e- total, Neff=21.22.7,KEK, May 9th, 2007,P. Colas - TPC R&D,21,Resolution measurement B=0,r.m.s. of the residuals (swithswo)2 methods for the track: global likelihood fit or c2 fit,Note: bias at small z - the track is r
23、econstructed close to the middle of the central pad (hollow points),KEK, May 9th, 2007,P. Colas - TPC R&D,22,Resolution measurement B=0.5 and 1T,KEK, May 9th, 2007,P. Colas - TPC R&D,23,KEK, May 9th, 2007,P. Colas - TPC R&D,24,KEK, May 9th, 2007,P. Colas - TPC R&D,25,Taking the finite pad width into
24、 account, K. Fujii derived a fully analytic formula for the resolution,KEK, May 9th, 2007,P. Colas - TPC R&D,26,Scaling,(use dimensionless quantities scaled by the pad width w)The resolution dependance on z has two regimes: At large z the asymptotic behaviour follows the diffusion limitAt low z the
25、effect of finite pad size dominates.For typical values of Neff, the optimal resolution is about 10% of the pad size.,1/12,1/(12.Neff),KEK, May 9th, 2007,P. Colas - TPC R&D,27,Achievements,With charge spreading, the resolution was measured to be 50 microns at low z(and at all z for large enough B fie
26、ld),KEK test beamMicromegas with resistive foil,KEK, May 9th, 2007,P. Colas - TPC R&D,28,Extrapolation to ILC-TPC,Conclusion: even with 1mm pitch, Micromegas with standard pads would not quite fulfill the requirement of better than 130 micron point resolution. However with a resisitive foil and 2.3
27、mm pads, this goal is largerly attained (red curve).,KEK, May 9th, 2007,P. Colas - TPC R&D,29,Achievements,Broken record on the 55Fe line resolution (5.6%),KEK, january 2007,threshold200 eV!,KEK, May 9th, 2007,P. Colas - TPC R&D,30,Work in progress and plans,Large Prototype : a world collaboration b
28、y LC-TPC, using the EUDET infrastructurePCMAG Magnet lend by KEK, associate to the EUDET project. Installed in DESY in December 2006CDC group, Canadian group, Tsinghua are responsible for the GEM panels. Saclay, Orsay and Carleton are responsible for the Micromegas panels = as much as possible devel
29、opment in commonA. Sugiyama and PC are coordinating GEM and Micromegas panelsA test of operation of GEMs and Micromegas with neutrons is necessary and the France-Japan collaboration explores this possibilityIn 2008-2009, we will take data together at DESY in the PCMAG magnet, do the analysis togethe
30、r, in the scope of choosing the technology.,KEK, May 9th, 2007,P. Colas - TPC R&D,31,Large Prototype panels,f = 80cm,D. Peterson, Cornell,Saga GEM prototype panel(3700 channels),KEK, May 9th, 2007,P. Colas - TPC R&D,32,Summary,We maintained a privileged french-japanese axis in the worldwide collabor
31、ation for a Linear Collider TPCThis was the backbone of the Micromegas TPC beam testsThis collaboration was very fruitful and lead to a detailed understanding of the fundamental limitations on the resolution of a Micropattern TPC.In the near future, we should bring a major contribution to the Large Prototype design and construction.,
