Download Measuring difficult reaction rates involving

Measuring difficult reaction rates
involving radioactive beams: A new
approach
John D’Auria, Mats Lindroos,
Jordi Jose and Lothar Buchmann
Mats Lindroos
Scientific Rationale
Nuclear Astrophysics/Reactions in Exploding Stars
• Key Reaction Rates needed to elucidate processes
• Low Reaction Probabilities
• Inverse kinematics is required
• Require Intense Radioactive Beams (>108 /s)
• Require beams of good properties
– high purity
– good emittance
– low velocities
• ISOL approach is the optimal production method
However, there are some beams which are very
difficult beams to produce by the ISOL method:
Mats Lindroos
Examples
30P(p,)31S
:
Determines the path through Si-Ca region in novae,
Important for understanding 30Si content in
presolar grains
15O(alpha,)19Ne:
Key reaction for breakout of CNO cycle
leading to rp process in X-Ray bursts.
Need to know ignition temperature, not limit.
(Need about 1011 /s to do proper study)
25Al(p,)26Mg:
Important for the synthesis of 26Al,
a radioisotope observed in galaxy.
Contributions from secondary sources (such as novae)
is not well established.
These are difficult beams to produce with high intensities!
(And there are more reactions like these)
Mats Lindroos
What has already been done?
•
30P(p,)31S
: Indirect studies to improve knowledge of levels ~ 1 MeV
- 32S(p,d)31S ; 31P(3He,t)31S(p)30P  new levels
- -decay of 31Cl to 31S (p decay)  new levels
- HI rxs. populating levels in 31S  (p, ) estimate
- Based on models, rate is higher than now believed.
Re-evaluation of the 30P(p,)31S astrophysical reaction
rate from study of the T=1/2 mirror nuclei, 31S and 31P,
D. Jenkins et al, Phys. Rev. C, In press
•
15O(alpha,)19Ne:
•
25Al(p,)26Mg:
-
Indirect studies to put limit on reaction rate
Key resonance state is at ER = 504 keV (Ex=4033 keV)
Limit on rate using (p,t) inverse kinematics (<.13meV)
Breakout does not occur in classical nova
Need breakout temperatures for X-Ray Bursts
Many indirect transfer reactions studies
- Studies at HRIBF, LLN, and elsewhere
- Some difference in spins, strengths and energies of key
states
Mats Lindroos
25Al(p,)26Si
•
•
•
•
•
•
Only indirect studies have been performed to measure , deduce 
Recent references (transfer reactions) include
- A. Parikh, et.al., PRC 71 (2005) 055804 [YALE]
- J. Caggiano, et.al., PRC 65 (2002) 055801 [YALE]
- Y. Parpottas, et.al., PRC 70 (2004) 065805 [Ohio]
- D. Bardayan, et.al., PRC 65 (2002) 032801 (R) [HRIBF]
Some dispute on key states/resonances (energy, spin, strength)
New mass measurement of 26Si (effects resonance energy)
Ex J ER

Ex J
ER

5672 1+ 159 1.1 neV
5670 1+ 152 32.5 nev
5915 0+ 403 .41 meV
5912 3+ 394 0.19 meV
5946 3+ 434 .19 meV
5946 0+ 428 0.505 meV
Need to develop intense (pure) beams
- Present SiC ISOL target does not release aluminum
sufficiently fast to allow optimal extraction of aluminum reaction
products leading to beams of 25,26mAl.
Mats Lindroos
A new approach
Beam cooling with ionisation losses – C. Rubbia, A Ferrari,
Y. Kadi and V. Vlachoudis in NIM A, In press
“Many other applications in a number of different fields
may also take profit of intense beams of radioactive ions.”
7Li
6Li
7Li(d,p)8Li
6Li(3He,n)8B
Missed opportunities
See also: Development of FFAG accelerators and their applications for
Mats Lindroos
intense secondary particle production,
Y. Mori, NIM A562(2006)591
Transverse cooling in paper by Carlo Rubbia et al.
“In these conditions, like in the similar case of the synchrotron
radiation, the transverse emittance will converge to zero. In
the case of ionisation cooling, a finite equilibrium emittance
is due to the presence of the multiple Coulomb scattering.”
Mats Lindroos
Longitudinal cooling in paper by Carlo Rubbia et al.
“In order to introduce a change in the dU/dE term — making it positive in order
to achieve longitudinal cooling — the gas target may be located in a point of
the lattice with a chromatic dispersion. The thickness of the foil must be
wedge-shaped in order to introduce an appropriate energy loss change,
proportionally to the displacement from the equilibrium orbit position.”
Number of turns
Mats Lindroos
1)
Without wedge, dU/dE<0
2)
Wedge with dU/dE=0, no
longitudinal cooling
3)
Wedge with dU/dE=0.0094
4)
Electrons, cooling through
synchrotron radiation
Inverse kinematics production and ionisation parameters in paper by
Carlo Rubbia et al.
7Li(d,p)8Li
6Li(3He,n)8B
Mats Lindroos
Collection in paper by Carlo Rubbia et al.
“The technique of using very thin targets in order to produce secondary
neutral beams has been in use for many years. Probably the best
known and most successful source of radioactive beams is ISOLDE.”
+/- 8V
500A
Protons
*
+/- 9V
1000A
Mats Lindroos
Reactions of interest for our application
•
27Al(alpha,n)30P
•
14N(2H,n)15O
•
?
– D.J.Frantsvog et al, PRC 25(1982)770: 8.8-15.8 MeV, 480(50) mb
?
– S.Takacs et al, NIM/B,211(2003) 169
24Mg(3He,2H)25Al
?
– D.J.Frantsvog et al, PRC 25(1982)770: 7.2-15.3 MeV, 430(70) mb
Mats Lindroos
Collection in a gas cell
• IGISOL technique (Ion Guide)
Cool gas in
Gas cell
BEAM
Extraction
•Figure from Juha Aysto, Nucl.Phys. A693(2001)477
•At 200 Torr of 4He, 10% efficiency, space charge limit at
108 ions cm-3 (peak 1010 ions cm-3?), Private communication
Ari Jokinen
Mats Lindroos
What about the intensities?
– Cross section similar or larger compared to
those studied in detail in C. Rubbia et al.’s paper
– The production should exceed the required
intensities (max. 1011 ions s-1)
– Heavy ions in the ring will require further beam
dynamics study
– Space charge effects will set the limit for the
IGISOL type device. With a 1000 cm3 gas cell,
is 1011 ions s-1 realistic?
– Collection with foils as proposed by C. Rubia et
al?
– Standard experimental techniques for the
experiment e.g. ISAC and REX-ISOLDE.
Mats Lindroos
Experiment:
HIE-ISOLDE
Laser Cabin
QP1
M1
Pr1
Pr2
OPTICAL PATH:
18 m to GPS
23 m to HRS
Pr3
Pr4
M2
QP2
CCD1
CCD2
M4
QP4
M5
DG
SC
Pr5
Mass separator
Power meter
HIGH VOLTAGE
r
BUFFER GAS
VDC(z)
z
Mats Lindroos
EURISOL DESIGN STUDY
EURISOL Town meeting at CERN:
27-28 November 2006!
Mats Lindroos
http://eurisol.org