direct measurement of 12 c + 4 he fusion cross section at ecm=1.5mev at kutl
DESCRIPTION
Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL. H.Yamaguchi K. Sagara, K. Fujita, T. Teranishi, M. taniguchi, S .Liu, S. Matsua, Maria T. Rosary, T. Mitsuzumi, M. Iwasaki K yushu U niversity T andem accelerator L aboratory. 2010. 1990. 1970. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/1.jpg)
Direct measurement of 12C + 4He fusion cross section at Ecm=1.5MeV at KUTL
H.Yamaguchi K. Sagara, K. Fujita, T. Teranishi, M. taniguchi, S .Liu, S. Matsua, Maria T. Rosary, T. Mitsuzumi, M. Iwasaki
Kyushu University Tandem accelerator Laboratory
![Page 2: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/2.jpg)
H-burning
4p → 4Hevia
p-p chain &CNO cycle
He-burning
3 4He → 12C
C-burning
O-burning Si-burning
Burning process in stars
12C/16O ratio affects widely further nuclear synthesis.
4He+12C → 16O+γ cross section has not been determined yet, in spite of 40 years efforts in the world.
C. Rolfs (Ruhr Univ.) Kyushu U.
world
goal
20101970 1990
+ +
α 4α3α
~40 years
17 years
4He+12C → 16O+
4He+12C → 16O+γ experiment is very difficult.
4He + 12C → 16O +
![Page 3: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/3.jpg)
E1 E2
Why is 4He+12C→16O+γ experiment so difficult?
Really low-energy experiments near 0.3MeV are necessary to make reliable extrapolation.
• At 0.3MeV 4He(12C,16O)Cross Section isvery small (~10-8 nb) due to Coulomb repulsion
Cross section (S=const.)
10-5
10-5
0.70.3 2.40.3
stellar energy
Coulomb-barrier effect
Extrapolation
Experiments
Experiment
![Page 4: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/4.jpg)
Experimental methods for 4He+12C→16O+γ cross section
![Page 5: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/5.jpg)
→ γ
Stellar energy
4He+12C→16O+γ experiment with γ detection
S-factor has not been precisely determined yet.
Cross section (S=const.)
10-5
10-5
Coulomb barrier effectNo precise data at low energy due to ・ low detection-efficiency of γ-rays ・ huge Back Ground (BG) γ-rays
![Page 6: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/6.jpg)
Experimental methods for 4He+12C→16O+γ cross section
high detection efficiency (~ 40%: charge fraction)total S-factor can be measured
![Page 7: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/7.jpg)
③②①
Yield of 12C + 4He → 16O + γ
Y(16O) = ・ N(12C) ・ N(4He ) ・ Detection Efficiency ・ Beam Time
・ necessary components for Ecm=0.7MeV experiment- high intensity 12C beam: ~ 10 pA ( Limit of our tandem accelerator )- Thick windowless 4He gas target : ~20 Torr x 4 cm (Limit of E in the target )- high detection efficiency (~40%)
・ Y(16O) ~ 5 counts/day at Ecm=0.7MeV → 1 month exp.
Background (BG) reductionN(16O)/N(12C) ~ 10-18 N(BG) / N(12C) < 10-19
beam target detect
Cross section (S=const.)
10-5
10-5
0.70.3 2.4
Increase the yield
at Ecm = 0.6 MeV → 10 month exp.at Ecm = 0.3 MeV → 7,000 year exp
Very hard to realize
Cross section is very small
extrapolate experiment
![Page 8: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/8.jpg)
Setup for 4He(12C,16O)Experimentat Kyushu University Tandem Laboratory (KUTL)
Detector (Si-SSD)
Sputterion source
12C beam
Tandem Accelerator
Final focal plane(mass separation)
Blow in windowless4He gas target
Long-time chopper
chopperbuncher
16O
12C
Recoil Mass Separator(RMS)
Ecm = 2.4~0.7 MeVE(12C)=9.6~2.8 MeVE(16O)=7.2~2.1 MeV
Tandem
RMS
E-def
D-mag
D-mag
![Page 9: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/9.jpg)
normal operation
accel-deceloperation
Al shorting bars for accel-decel operation
Accel-decel operation of tandem accelerator
Y(16O) = ・ N(12C) ・ N(4He ) ・ Det.Efficiency ・ Beam Time
At low acceleration voltage, focusing becomes weak, and beam transmission decreases.By alternative focus-defocus, focusing becomes strong, and beam transmission increases. ・ 10 times higher beam transmission is obtained by strong focusing. ・ 10 times more intense beam can be injected.
①Increase the 12C beam
Totally, beam intensity is ~100 times increased
![Page 10: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/10.jpg)
RMS
TMP3
TMP4MBP2TMP2TMP5
MBP1
beam
TMP1
DP
1500 l/s
3000 l/s330 l/s
330 l/s520 l/s 520 l/s
520 l/s
350 l/s
Windowless Gas Target
Differential pumping system (side view)
• center pressure: 24 Torr center pressure: 24 Torr • effective length: 3.98 ± 0.12 cm (measured by p+α elastic scattering)effective length: 3.98 ± 0.12 cm (measured by p+α elastic scattering)
→ → target thickness is sufficient for our experimenttarget thickness is sufficient for our experiment (limited by energy loss of (limited by energy loss of 1212C beam)C beam)
SSD: beam monitor4.5cm
• Blow-In Gas Target (BIGT)– windowless & high confinement capability
beam
Y(16O) = ・ N(12C) ・ N(4He ) ・ Det.Efficiency ・ Beam Time
②Increase the 4He gas target
Thickest in the world
24Torr
![Page 11: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/11.jpg)
③②①
Recoil Mass Separator
All the 16O recoils(±2°) in a charge state (~40%) are detected.
12C + 4He → 16O +γ yield has been increased
Y(16O) = ・ N(12C) ・ N(4He ) ・ Detection Efficiency ・
Beam Time
③Increase the 16O detection efficiency
12C + 4He → 16O +γ
12C beam
4He windowless Gas target
Eject within 2°
16O
E-def
D mag
D magdetect 16O5+
![Page 12: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/12.jpg)
RF-Deflector
BG reduction
• Background 12C are produced bymultiple scatteringcharge exchange
• Background reduction ・ Recoil Mass Separator background reduction ~10-11
・ TOF with Pulsed beam ~10-2
・ Long-Time Chopper(RF deflector) ~10-3 N(BG)/N(16O) become 10-16
Goal: N(BG)/N(12C) < 10-19
At present:
N(16O)/N(12C) ~ 10-18 at 0.7MeV
E-def D mag
D magLTC
![Page 13: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/13.jpg)
pass only reaction products (16O) which are spread in time.
f2=3×f1
V2=V1/9
f1=6.1MHzV1=±24.7kV
V3=23.7kV
reject BG
Pass
16O
+
Flat-bottom voltage
Long-Time Chopper(RF deflector)
BG(12C)16O5+
500events
Measurement of 4He(12C,16O)γ at Ecm = 2.4 MeV
BG reduction
RF-Deflector
LTC
without LTC with LTC
![Page 14: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/14.jpg)
14
4He(12C,16O)at Ecm=2.4MeV experiment• beam: 12C2+, frequency: 6.063MHz
– energy: 9.6MeV , intensity: ~35pnA• target: 4He gas ~ 23.9 Torr x 3.98 cm• observable: 16O5+ 7.2 ± 0.3 MeV
– abundance = 36.9 ± 2.1 % = efficiency
29hours data29hours data
941 counts
16O
![Page 15: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/15.jpg)
• 2.4MeV–
4He(12C,16O)at Ecm=2.4MeV experiment
Our data
bkeV 3.889.0S(2.4) nb, 2.764.6
Ruhr univ.
![Page 16: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/16.jpg)
4He(12C,16O)at Ecm=1.5 MeV experiment• beam: 12C1+, frequency: 3.620MHz
– energy: 6.0MeV, intensity: 60pnA
• target: 4He gas 15.0 Torr x 3.98 cm• observable: 16O3+, 4.5 ± 0.3 MeV
– abundance = 40.9 ± 2.1 % = efficiency
208 counts208 counts
95 hours data95 hours data
16O
![Page 17: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/17.jpg)
Ruhr U.Kyushu U.
extrapolation
Cross Section and Stot-factor
• 1.5MeV–
• Next experiment is Ecm=1.151.00.850.7 MeV
bkeV 2.826.6S(1.5) nb, 0.090.900
Stellar energy
Our exp. plan
preliminary
![Page 18: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/18.jpg)
Further BG reduction is necessary95 hours data95 hours data
16O
In order to go to low energy further BG Reduction is necessary!
Ecm=2.4MeVσ ~ 65nb
Increased BG 1.5MeVσ ~ 0.7nb
down to 0.7MeV
![Page 19: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/19.jpg)
• measure the ΔE (∝ energy loss) by the ionization chamber (and E by the SSD)
further BG reduction
We can separate 16O from BG (12C)
16O
12C
4He
16O
BG reject
16O and 12C separation by Ionization chamber
-
+
cathode
anode
PR Gas 30Torr
very thin foil (0.9μm)
16O,12Ce -
Si-SSD
e - e - e -
ΔE E
low energy
ΔE of 16O is larger than 12C
![Page 20: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/20.jpg)
BG reduction by Ionization Chamber
95 hours data95 hours data
Huge 12C-BG will be eliminated using the ionization chamber.
Ionization chamber will be available from October 2011.
16O
12C
4He
16O
BG reject
16O
![Page 21: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/21.jpg)
Summary• Direct measurement of 4He+12C 16O+γ cross section (total S-factor) is in
progress at KUTL (Kyushu Univ. Tandem Lab.)
• Many new instruments and methods have been developed for this experiment.
• Ecm= 2.4 MeV experiment– = 64.6 nb, – S-factor = 89.0 keV b
• Ecm= 1.5 MeV experiment– = 0.900 nb,– S-factor = 26.6 keV b
• Now we are developing an ionization chamber.
• Experiments of 4He+12C 16O+γ at Ecm = 1.51.151.00.850.7MeV will be made in a few years.
future plan
, 2010
stellar energy
Stellar energy
![Page 22: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/22.jpg)
)]/([
|)(1|
|)]/([|)12(
2
22/12/1
EER
RiPRBS
EEl
k
lll
lllll
lllEl
R.Kuntz, M.Fey, M.Jaeger, A.Mayer, W.Hammer Astrophysical J. 567. (2002) 643 - 650
A rehearsal for extrapolation using R-matrix theory
Ecm [ MeV ]0.700.851.001.151.50
S-factor [ keV b ]70.0±7.050.0±5.045.0±4.535.0±3.530.0±3.0
Assumed data (±10%)
Data from Ruhr university
Assumed data
S(0.3MeV) extrapolated = 190±15 keV b1 -2 +
0.3
Reliable theoretical curve will be
necessary for extrapolation
++
![Page 23: Direct measurement of 12 C + 4 He fusion cross section at Ecm=1.5MeV at KUTL](https://reader036.vdocuments.mx/reader036/viewer/2022062409/5681518b550346895dbfc37b/html5/thumbnails/23.jpg)