Mats Lindroos

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 cycleleading 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: 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

• 25Al(p,)26Mg: 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(d,p)8Li6Li(3He,n)8B

7Li6Li

Missed opportunities

See also: Development of FFAG accelerators and their applications for intense secondary particle production, Y. Mori, NIM A562(2006)591

Mats Lindroos

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

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

Mats Lindroos

Inverse kinematics production and ionisation parameters in paper by Carlo Rubbia et al.

7Li(d,p)8Li6Li(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.”

Protons

+/- 8V500A

+/- 9V1000A

*

Mats Lindroos

Reactions of interest for our application

• 27Al(alpha,n)30P ?– D.J.Frantsvog et al, PRC 25(1982)770: 8.8-15.8 MeV, 480(50) mb

• 14N(2H,n)15O ?– 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)

•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

BEAMGas cell

Extraction

Cool gas in

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

BUFFER GAS

HIGH VOLTAGE

VDC(z)

z

r

QP2

OPTICAL PATH:18 m to GPS23 m to HRS

M1

Pr1

Pr2

Pr3

M5

M2

Laser Cabin

Pr4

SC

QP1

DG

CCD2CCD1

M4

QP4

Power meter

Pr5Mass separator

Mats Lindroos

EURISOL DESIGN STUDY

EURISOL Town meeting at CERN: 27-28 November 2006! http://eurisol.org