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 (>10 8 /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 30 P(p,  ) 31 S : Determines the path through Si-Ca region in novae, Important for understanding 30 Si content in presolar grains 15 O(alpha,  ) 19 Ne:Key reaction for breakout of CNO cycle leading to rp process in X-Ray bursts. Need to know ignition temperature, not limit. (Need about /s to do proper study) 25 Al(p,  ) 26 Mg:Important for the synthesis of 26 Al, 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? 30 P(p,  ) 31 S : Indirect studies to improve knowledge of levels ~ 1 MeV - 32 S(p,d) 31 S ; 31 P( 3 He,t) 31 S(p) 30 P  new levels -  -decay of 31 Cl to 31 S (p decay)  new levels - HI rxs. populating levels in 31 S  (p,  ) estimate - Based on models, rate is higher than now believed. Re-evaluation of the 30 P(p,  ) 31 S astrophysical reaction rate from study of the T=1/2 mirror nuclei, 31 S and 31 P, D. Jenkins et al, Phys. Rev. C, In press 15 O(alpha,  ) 19 Ne: Indirect studies to put limit on reaction rate -Key resonance state is at E R = 504 keV (E x =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 25 Al(p,  ) 26 Mg: Many indirect transfer reactions studies -Studies at HRIBF, LLN, and elsewhere -Some difference in spins, strengths and energies of key states

Mats Lindroos 25 Al(p,  ) 26 Si Only indirect studies have been performed to measure , deduce  Recent references (transfer reactions) include - A. Parikh, et.al., PRC 71 (2005) [YALE] - J. Caggiano, et.al., PRC 65 (2002) [YALE] - Y. Parpottas, et.al., PRC 70 (2004) [Ohio] - D. Bardayan, et.al., PRC 65 (2002) (R) [HRIBF] Some dispute on key states/resonances (energy, spin, strength) New mass measurement of 26 Si (effects resonance energy) E x J  E R  E x J  E R  neV nev meV meV meV 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 25,26m Al.

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.” 7 Li(d,p) 8 Li 6 Li( 3 He,n) 8 B 7 Li 6 Li 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= )Electrons, cooling through synchrotron radiation

Mats Lindroos Inverse kinematics production and ionisation parameters in paper by Carlo Rubbia et al. 7 Li(d,p) 8 Li 6 Li( 3 He,n) 8 B

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.”

Mats Lindroos Reactions of interest for our application 27 Al(alpha,n) 30 P ? –D.J.Frantsvog et al, PRC 25(1982)770: MeV, 480(50) mb 14 N( 2 H,n) 15 O ? –S.Takacs et al, NIM/B,211(2003) Mg( 3 He, 2 H) 25 Al ? –D.J.Frantsvog et al, PRC 25(1982)770: 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 4 He, 10% efficiency, space charge limit at 10 8 ions cm -3 (peak ions cm -3 ?), Private communication Ari Jokinen BEAM Gas 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 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 cm 3 gas cell, is 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

Mats Lindroos EURISOL DESIGN STUDY EURISOL Town meeting at CERN: November 2006!