Maria Theodora Rosary, 相良建至, 寺西高, 藤田訓裕, タンデム加速器の加速減速強集束運転法 Acceleration-Deceleration STRONG FOCUSING operation OF Tandem Accelerator Maria Theodora Rosary, 相良建至, 寺西高, 藤田訓裕, 谷口雅彦, 大場希美, 松田沙矢香, 山口祐幸 九州大学大学院理学府理学専攻粒子物理学

Introduction Astrophysics Experiment : 12C + 4He → 16O + γ We need Stellar energy Exp. plan D. Schurmann et al. Eur. Phys. J. A 26, 301-305 (2005) We need Ecm [MeV] Beam intensity Target Yield [/day] Time 2.4 50pnA 6Torr x 4.5cm 420 1.5 100pnA 15Torr x 4.5cm 150 1.15 1pμA 20Torr x 4.5cm 300 1.0 2pμA 100 0.85 20 2 weeks 0.7 10pμA 5 1 month 2014 2012 2010

Experiment At Ecm = 1.15  0.7 MeV Vac 12C 16O Detector (Si-SSD) Sputter ion source & pre-buncher 12C beam Tandem Accelerator 16O 12C Acceleration Voltage (Vac) (MV)

Experiment How to do ? Iin Iout At Ecm = 1.15  0.7 MeV We need high intensity 12C beam (10A) But beam transmission (Tr) is low Tandem Accelerator Vac (MV) Iin Iout How to do ? Beam Transmission Focusing force is strong Focusing force is weak Vac

Acceleration–Deceleration Operation Year 2002 Kyushu University Normal Accel-Decel add shorting bars Vac Vac 1MV Focusing force is weak 6MV Focusing force is strong Accel-Decel operation (strong focusing) Normal operation (weak focusing) Iac Iac Iac Iac Iac Vac (MV) Vac (MV) Vac (MV) In calculation, beam transmission (Tr) was increased Experiment using 1MV  Beam transmission (Tr) was 10 times increased  Injected beam current can be increased Total : beam intensity was nearly 200 times increased

The problem Beam load for accelerator Beam Envelope (Now) e-  load Gas stripper 20pA 10pA 12C- Beam fluctuates  Load fluctuates Vac is unstable … feedback Beam is unstable Beam hits acceleration tube  Many secondary e- are generated Become load Beam Envelope (Now) Beam Envelope (Optimum) Not hit Beam Large load Small load Hit How to reduce beam load ?

The Problem Beam Envelope (Now) Beam Envelope (Optimum) Large load Not hit Beam Large load Small load Hit

Project Make focus-simulation program  Reproduce previous simulation Calculate with realistic distribution voltage Earthquake (2005)  some glass columns were cracked and electrically shorted Search for small-load (Optimum Vac distribution)

Focus Calculation rf = 5 mm (at the stripper) rmax =10 mm (in the acceleration tube) Vac 20 tubes Vac L = acceleration tube length fi and fo = focal length D = drift space length a = 1.0 and b = 0.57 r = radius  = angle X 20 tubes Condition : r20 ≤ 5 mm (at the stripper) r1-r19 ≤ 10 mm (in the acceleration tube) Acceptance  r1.1 Beam transmission (Tr)  (r1.1)2

Result Normal reproduce Accel-Decel Ideal Accel-Decel Realistic Acceleration voltage Beam profile on acceleration tube Normal reproduce Accel-Decel Ideal Accel-Decel Realistic Earthquake damage was small Tr(1MV) = 1 Tr (6MV) 5.49 Tr(AD ideal) =13.44 Tr (Normal) Tr(AD real) =0.97 Tr (AD ideal)

Thank YOU Summary Finished Project : Make focus-simulation program Reproduce previous simulation Calculate with realistic distribution voltage Earthquake (2005)  some glass columns were cracked and electrically shorted Search for small-load (Vac distribution) Finished Not hit Beam Small load To minimize beam load, optimum Vac distribution will be searched from now. For 12C+4He  16O+  experiment below Ecm = 1.15 MeV, Accel-Decel operation is necessary. New Accel-Decel simulation program has been prepared. Thank YOU