Research on a new crystal-assisted positron source for the ILC このプレゼンテーションでは、出席者間で討論をし、アクション アイテムを作成する場合があります。PowerPoint を使って、プレゼンテーションの実行中にアクション アイテムを作成するには ... スライド ショーの実行中に control + クリック [会議メモ] をクリック [アクション アイテム] タブをクリック アクション アイテムを入力 [OK] をクリック このようにすると、入力したアクション アイテムを集めたスライドが、プレゼンテーションの最後に自動的に作成されます。 A_R&D_06 proposal T.Suwada (tsuyoshi.suwada@kek.jp) Accelerator Laboratory, KEK Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Collaboration Japanese Group K.Furukawa, T.Kamitani, T.Omori, M.Satoh, T.Suwada, J.Urakawa, Accelerator Laboratory, KEK K.Umemori, IMSS, KEK T.Takahashi, S.Kawada, Y.Uesugi, Hiroshima University French Group A.Variola, O. Dadoun, F. Poirier, I. Chaikovska, LAL-Orsay R.Chehab, X. Artru, M. Chevallier, IPNL-Lyon with collaboration of V. Strakhovenko , BINP-Novosibirsk Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Introduction It is a challenge task to construct a dedicated and also robust positron source towards the next generation of e+e- linear colliders. The present RDR-based ILC e+ (positron) source uses photo-production from a long helical undulator to generate positrons. A crystal-assisted positron source would be another approach to ILC. Successful tests on a positron source using channeling radiation in crystals were performed at CERN (WA 103) and KEK. An hybrid scheme based on the separation between the crystal-radiator and the amorphous converter has been adopted for the CLIC positron source. We propose that the feasibility studies based on this new scheme need to be conducted under powerful collaboration between France and Japan. Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

An atomic undulator for the generation of unpolarized positrons for CLIC and ILC An hybrid source using an atomic undulator (first proposition for a crystal source, Proceedings of PAC, Chicago, 1989) R.Chehab, A.Artru, F.Couchot, A.R.Nyaiesh, F.Richard Simulations of a hybrid source made of Ge or Si crystals as radiators and amorphous W as converters: For Ge and Si crystals oriented on <110> axis and 1 cm thick, we had e+ accepted yields of 0.5 to 0.6 e+/e- for 0.5 Xo thick converter and 1.2 to 1.3 e+/e- for 1 Xo thick; the incident e- energy is 20 GeV R. Chehab, POSIPOL2010, KEK, June2010 Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

New hybrid target scheme for positron production THE HYBRID SCHEME FOR FUTURE LINEAR COLLIDERS Assuming thin crystal target and, hence, moderate heating in it and in order to lower the amount of energy deposited in the amorphous target and also the PEDD, the following scheme has been proposed by [R.Chehab, V.M.Strakhovenko, A.Variola] This new scheme is the basis of the present common research between France and Japan. Magnet Putting a drift between the 2 targets allows sweeping off the charged particles coming from the crystal; only the ϒ impinge on the amorphous target R. Chehab, POSIPOL2010, KEK, June2010 Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Development of simulation code at LAL-Orsay + X. Artru simulation The present work is consisting in the combination of X. Artru’s program on channeling with GEANT4. The new program will be used for extended simulations and for the KEKB experiment (data analysis). O. Dadoun, POSIPOL2010, KEK, June2010 Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Experimental status at KEK The purpose is the experimental evaluation for the hybrid-target scheme. Particularly, to estimate the positron-production efficiency, and to evaluate the heat load on a hybrid target. The positron-production experiments based on a hybrid target has been continued with 8-GeV e- beam at KEK and the systematic studies were carried out on the positron-production efficiency in 2010. The experiments on the heat load with a hybrid target has been continued from 2011, and however, they have been carried out as only a test experiment with 3-GeV e- beam due to the Tohoku heavy earthquake. Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Experimental site at KEKB LINAC Switchyard KEKB Linac 8-GeV　e- beam 1nc/bunch upto 25Hz single bunch Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Site Set up at the KEK Linac Looking up from Down stream Max. Ee-=8GeV Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France 9

This is the beginning of the earthquake (11 Mar.2011). Long (~3 minutes) and strong (6 lower in Japanese scale) earthquake we never experienced! KEK Tohoku area hypocenter ~0.2 s (~5 Hz) K-Netによる加速度の観測 (防災科学技術研究所提供） 342.9 gal 328.8 gal Tsukuba Tsukidate Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Drop-down of a quadrupole triplet and the recovery work is in progress! Beamline Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Experimental Setup based on the hybrid target scheme amorphous W 8 mm 18 mm 8GeV e- Sweeping Magnet 0.96T 0.75m Analyzing magnet 5 ~ 30MeV 1mm thick W crystal Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

pictures e- 8GeV Sweeping magnet W Crystal on the goniometer Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

pictures thermocoupoles attached back end amorphous targets Amorphous Ws mounted on a linear stage movable stage Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Experimental scheme Hybrid scheme Conventional scheme e- 8GeV γ positrons from the target momentum analyzed Amorphous W sweep mag 1mm-thick W Crystal on axis (aligned to the beam) off axis (not aligned to the beam) temperature at the end of the targets by thermocouples and infrared camera Amorphous W e- 8GeV amorphous Ws 1.75, 3.5, 5.25, 8, 18mm Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Rocking curve measurement Amorphous W 8-GV e- sweep magnet Crystal W on a goniometer 8 mm rotation in ver. plain Fitting function for the rocking curve Preliminary factor 3 enhancement positron yield (arb. unit) [mrad] angle of crystal　axis<111> w.r.t. beam (mrad) Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Positron yield measurement Ee- = 8 GeV, Pe+ = 20 MeV e+ detected [a.u] amorphous W thickness [mm] Need more simulations for analyzing the magnet collimator , detector to evaluate e+ yields Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Temperature Measurement with 8-GeV e- beam Temperature of the 8mm amorphous W target for the hybrid case Beam charge ~1nC/bunch, 25Hz Preliminary Temperature (degree Celsius) ΔT~32 degree Base temp. 23.3deg. Time from Beam On (Minutes) Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Temp. rise vs. total energy deposit Temperature at equilibrium has information for total energy deposit except for 18mm hybrid (measured) conventional 18mm hybrid　on axis target thickness is larger than shower maximum hybrid off axis T at equilibrium (deg.) 8mm (simulation)

Development of a thermocouple array to measure temperature rise of the target Thermocouple array fixed at the back plane of amorphous target Thermocouple 1mm x 1mm to fast data logger read temperature each 10ms temperature at equilibrium 9 thermocouples are fixed on the target with use of silver paste total energy deposit bunch by bunch temperature variation PEDD information by thermocouple Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Test results on pulse-by-pulse Temp. rise measurement (3-GeV e- beam) 3-GeV e- single-bunch beam is directly hitting at the center of target. The pulse-by-pulse temp. measurement has been successfully performed at the rep. rate of 1Hz. A clear signal was obtained from each thermocouple. 2mm 1秒 1mm 1℃ 1s Clear temp. signal trace with a data logger has been obtained in a test measurement. Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

AN HYBRID TARGET TEST WITH GRANULAR CONVERTER POSIBLE DEVELOPMENTS ON THE HYBRID SOURCE In order to lower the heat load on the amorphous converter a particular shape for the amorphous converter was chosen. A granular converter made of small spheres (Φ= 2mm) has been investigated following the works of P.Sievers et al. on a target dedicated to a neutrino factory. The application for a positron source has been developed in the PhD thesis of Chenghai XU from IHEP/Beijing ,at LAL-Orsay. In such a scheme, the heat dissipation is improved. Different models have been studied and their merits concerning the e+ yield, the energy deposition and the PEDD (Peak Energy Density Distribution) , compared. As an example, for a granular converter made of 864 spheres of 2 mm diameter we get a total yield of 12.5 e+/e-, an energy deposition of 446 meV/e- and a PEDD less than 2 GeV/cm3/e-, somewhat better in terms of energy deposition than a compact converter giving the same yield. Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

An Hybrid target test with a granular converter PRESENTATION OF THE GRANULAR CONVERTER The granular converter made of staggered rows has been considered and its main features described (cf. article in Chinese Physics C) The best way of cooling being use of a He gas jet which removes the heat passing Between the spheres. To fulfill the requirements of ILC yield, 3 staggered rows (6 layers) of W spheres (Φ=2 mm) have been chosen (864 spheres). Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

AN HYBRID SOURCE TEST WITH A GRANULAR CONVERTER A granular converter might be thermally controlled with thermocouples and infrared cameras (see slides 20 &21). A comparison with a compact converter giving the same yield can, then, be operated. In a first step, the granular converter as the compact one will not be cooled during the test. thermocouples This test will be done in collaboration with IHEP/Beijing and CERN photons Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Funding requests in 2012 From French group Euro/unit Nb of units Total (Euro) PhD Student stay in France 1000/month 3 months 3000 Visit to Japan (2 visits) 150/day 10 days Travels (2) 1000 2 travels 2000 Total 8000 From Japan group kYen/unit Nb of units Total (kYen) Travel (3persons) 750 1 travels Visit to France(3persons) 60/day 10 days 600 Total 1350 Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France

Summary The systematic study on positron-production efficiency is in progress with 8-GeV e- beam at KEK. Test measurements with the thermocouple array detector have been preliminary conducted to evaluate pulse-by-pulse temperature rise with 3-GeV e- beam. The systematic simulations to estimate the detector acceptance are in progress with a new simulation code taking into account crystal effect. Due to unfortunate heavy earthquake, the recovery work of the KEKB linac is vigorously in progress. The perspective of testing an hybrid e+ source with a granular converter can open promising solutions for ILC. Tsuyoshi Suwada/KEKB Linac FJPPL Workshop 2012, 28-29 May 2012, Le L.P.C., Clermond-Ferrand, France