1. 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

2. Introduction Astrophysics Experiment : 12C + 4He → 16O + γ We need
Stellar energy
Exp. plan
D. Schurmann et al.
Eur. Phys. J. A 26, (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

3. 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)

4. 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

5. 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

6. 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 ?

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

8. 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)

9. 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

10. 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)
Tr(AD ideal) =13.44
Tr (Normal)
Tr(AD real) =0.97
Tr (AD ideal)

11. 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