1. Requirements for an Active Target
for FAIR
FAIR
Peter Egelhof
GSI Darmstadt, Germany
ACTAR Meeting Santiago de Compostela, Spain
March 10 – March 11, 2008

2. Requirements for an Active Target
for R3B at FAIR
FAIR
I. Introduction
II.   Perspectives and Experimental Conditions at FAIR
III. Requirements for an Active Target Setup
IV.   Conclusions

3. I. Introduction classical method to observe spectroscopic information:
 light ion induced direct reactions: (p,p), (p,p’), (d,p), … (before RIB-facilities: limited to stable nuclei)
aim: use radioactive beams from RIB-facilities for nuclear structure studies off stability method: Inverse Kinematics
proton-detector
beam of exotic
nuclei AX
1H (AX, 1H) AX
1H - target
first generation experiments:
mainly light neutron-rich nuclei (A  20)
only at external targets
extreme N/Z ratio  new phenomena of nuclear structure

4. The TPC-Ionization Chamber IKAR as Active Target
(provided by PNPI St. Petersburg)
detection principle: H2-target = detector for recoil protons
11Li P
11Li-beam from FRS
operating conditions:
H2-pressure: 10 atm
entrance window: 0.5 mm Berylium
target thickness: 30 mg/cm² (6 independent sections)
beam rate:  104/sec
but: method limited to Z  6!

5. Detection Principle of IKAR
11Li- projectile S TR Zv R z p
11Li
from pulse analysis: integral  recoil energy TR (EFWHM  90 KeV)
risetime  recoil angle R (FWHM  0.6°)
Start  vertex point ZV (zFWHM  110 m)

6. Investigation of Nuclear Matter Density Distributions of Halo Nuclei by Elastic Proton Scattering
Experimental Setup: Active Target IKAR and Aladin Magnet
target + recoil detector: IKAR  TR,, R, ZV
trajectory-reconstruction: PC 1-4 (Multiwire proportional chambers)  S
beam identification: S 1-3, Veto (plastic scintillators)  E, TOF, trigger
ALADIN-magnet discrimination of position sensitive scintillator wall projectile breakup 

7. The IKAR Experimental Setup

8. Investigation of Nuclear Matter Density Distributions of Halo Nuclei by Elastic Proton Scattering at Low Momentum Transfer
data: IKAR-Collaboration
all experimental data are well described by Glauber calculations

9. Investigation of Nuclear Matter Density Distributions of Halo Nuclei by Elastic Proton Scattering at Low Momentum Transfer
nuclear matter
distributions:
nuclear matter
radii:
nucleus
Rmatter, fm
Rcore, fm
Rhalo, fm
4He
1.49 (3) --
8He
2.53(8)
1.55 (15)
3.08 (10)
9Li
2.43 (7)
11Li
3.62 (19)
2.55 (12)
6.54 (38)
 extended neutron distribution in 8He and 11Li obtained
 size of core, halo and total matter distribution determined with high accuracy

10. Elastic Proton Scattering from 8B
differential cross section:
deduced nuclear matter distribution:
 for the first time a proton halo was investigated
 the halo structure of 8B was confirmed
 the deduced matter radius Rm = 2.88 (13) fm is slightly larger as compared to previous results and theoretical predictions (Rm = fm)
 relevance for the astrophysical S(E) factor for the 7Be(p,γ)8B reaction ???
 to be investigated !!!

11. Perspectives at the Future Facility FAIR
FAIR: Facility for Antiproton and Ion Research
100 m
UNILAC
SIS 18
SIS 100/300
HESR
Super
FRS
NESR CR
RESR
GSI today
Future facility
ESR
FLAIR
Rare-Isotope
Production Target
Antiproton

12. FAIR: Facility Characteristics
Primary Beams
1012/s; GeV/u; 238U28+
Factor over present in intensity
2(4)x1013/s 30 GeV protons
1010/s 238U73+ up to 35 GeV/u
up to 90 GeV protons
Secondary Beams
Broad range of radioactive beams up to GeV/u; up to factor in
intensity over present
Antiprotons GeV
Cooled beams
Rapidly cycling superconducting magnets
Key Technical Features
Storage and Cooler Rings
Radioactive beams
e – A collider
1011 stored and cooled GeV antiprotons
100 m
UNILAC
SIS 18
SIS 100/300
HESR
Super
FRS
NESR CR
RESR
GSI today
Future facility
ESR
FLAIR
Rare-Isotope
Production Target
Antiproton

13. Nuclear Physics with Radioactive Beams at FAIR: NUSTAR: NUclear STructure, Astrophysics and Reactions
I High intensity primary beams from SIS 100 (e.g U / sec at 1 GeV/u)
II Superconducting
large acceptance
Fragmentseparator
III Three experimental areas
Optimized for efficient transport of fission products
SIS-100

14. Expected Production Rates
presently
known nuclei
r-process

15. Perspectives at the GSI Future Facility FAIR
known exotic nuclei
unknown exotic nuclei
pathways of stellar nucleosynthesis
regions of interest:
towards the driplines for medium heavy and heavy
nuclei
physics interest:
 matter distributions (halo, skin…)
 single-particle structure evolution (new magic numbers, new shell gaps, spetroscopic factors)
 NN correlations, pairing and clusterization phenomena
new collective modes (different deformations for p and n, giant resonance strength)
parameters of the nuclear equation of state
 in-medium interactions in asymetric and low-density matter
 astrophysical r and rp processes, understanding of supernovae       

16. Light-Ion Induced Direct Reactions at Low Momentum Transfer
elastic scattering (p,p), (,), … nuclear matter distribution  (r), skins, halo structures
inelastic scattering (p,p’), (,’), … deformation parameters, B(E2) values, transition densities, giant resonances
transfer reactions (p,d), (p,t), (p, 3He), (d,p), … single particle structure, spectroscopic factors, spectroscopy beyond the driplines, neutron pair correlations, neutron (proton) capture cross sections
charge exchange reactions (p,n), (3He,t), (d, 2He), … Gamow-Teller strength
knock-out reactions (p,2p), (p,pn), (p,p 4He)… ground state configurations, nucleon momentum distributions
for almost all cases:
region of low momentum transfer contains most important information

17. Experiments to be Performed at Very Low Momentum Transfer – Some Selected Examples
Investigation of Nuclear Matter Distributions along Isotopic Chains:  halo, skin structure  probe in medium interactions at extreme isospin (almost pure neutron matter)  in combination with electron scattering: separate neutron/proton content of nuclear matter method: elastic proton scattering  at low q: high sensitivity to nuclear periphery
Investigation of Giant Monopole Resonance in Doubly Magic Nuclei:  gives access to nuclear compressibility  key parameters of the EOS  new collective modes (breathing mode of neutron skin) method: inelastic  scattering at low q
Investigation of Gamow-Teller Transitions:  weak interaction rates for N = Z waiting point nuclei in the rp-process  electron capture rates in the presupernova evolution (core collaps) method: (3He,t), (d,2He) charge exchange reactions at low q

18. Proposed Experiments at FAIR
 investigation of nuclear matter distributions along isotopic chains towards proton/neutron asymmetric matter
 investigation of the same nuclei by (e,e) (ELISe) and (p,p) (EXL) scattering  separate neutron/proton content of nuclear matter  unambiguous and “model independent” determination of size and radial shape of neutron skins (halos)
theoretical prediction: P.-G. Reinhard
example: Sn isotopes at the nuclear surface: almost pure neutron matter  probe isospin dependence of effective in-medium interactions  sensitivity to the asymmetry energy (volume and surface term!)

19. The ELISe Experiment at FAIR ELISe: ELectron Ion Scattering in a Storage Ring e-A Collider
MeV electrons
MeV/u RIBs
spectrometer setup at the
interaction zone
nuclides of interest may
be studied by leptonic and
hadronic probes

20. Kinematical Conditions for Light-Ion Induced Direct Reactions in Inverse Kinematics
required beam energies: E  200 … 740 MeV/u (except for transfer reactions)
required targets: 1,2H, 3,4He
most important information in region of low momentum transfer  low recoil energies of recoil particles  need thin targets for sufficient angular and energy resolution
EXL
(,‘)
(p,p)
(3He, t)

21. Nuclear Reactions with Relativistic Radioactive Beams at FAIR
 R3B: Reactions with Relativistic Radioactive Beams  High Energy Branch
 EXL: EXotic Nuclei Studied in Light-Ion Induced Reactions at the NESR Storage Ring  Ring Branch

22. RIB‘s from the Super-FRS
EXL: EXotic Nuclei Studied in Light-Ion Induced Reactions at the NESR Storage Ring
Electron
cooler
eA-Collider
RIB‘s from the Super-FRS

23. Advantage of Storage Rings for Direct Reactions in Inverse Kinematics
 gain of luminosity due to: continuous beam accumulation and recirculation
 high resolution due to: beam cooling, thin target
 low background due to: pure, windowless 1,2H2, 3,4He, etc. targets
 separation of isomeric states
but: lifetime limit for very short lived exotic nuclei T1/2 ≥ 1 sec

24. RIB production Rates at FAIR

25. A universal setup for kinematical complete measurements of Reactions with Relativistic Radioactive Beams
The R3B experiment:
identification and beam "cooling" (tracking and momentum measurement, Dp/p ~10-4)
exclusive measurement of the final state:
- identification and momentum analysis of fragments
(large acceptance mode: Dp/p~10-3, high-resolution mode: Dp/p~10-4)
- coincident measurement of neutrons, protons, gamma-rays, light recoil particles
applicable to a wide class of reactions

26. An Active Target for R3B
 well suited as alternative technique to EXL for:
 short lifetimes (T ≤ 1 sec)
 low RIB intensities (≤ 105 sec-1)

27. The Active Target Setup at R3B

28. The Active Target Setup at R3B
Cylinder with Be windows 500 um
Beam shield d = 2 cm
Beam tracking + vertex reconstruction
Pressure P in the range 10 to 20 bar

29. Angular Region of Interest for (p,p) on Sn

30. Sensitivity on the Nuclear Radius

31. Kinematics

32. Kinematics

33. Dynamic Range

34. Energy Loss and Straggling

35. Required Angular Resolution

36. Required Energy Resolution

37. Count Rate Estimate

38. Lifetime including losses in NESR [s]
Predicted Luminosities
Target: 1014 H atoms cm-2; beam losses included
740 A.MeV
100 A.MeV
Nucleus
production
rate at S-FRS target
[1/s]
Lifetime including losses in NESR [s]
Luminosity [cm-2 s-1]
Luminosity
[cm-2 s-1]
(preliminary)
11Be
2 x 109 36
> 1028
46Ar
6 x 108 20
8 x 1026
52Ca
4 x 105 12
2 x 1026
4 x 1025
9 x 1023
55Ni
8 x 107
0.5
6 x 1026
5 x 1025
4 x 1010
56Ni
1 x 109
3800
5 x 1026
72Ni
9 x 106
4.1
2 x 1027
3 x 1026
2 x 1023
104Sn
1 x 106 51
3 x 1027
3 x 1025
132Sn
1 x 108 93
1 x 1027
134 Sn
8 x 105
2.7
5 x 1024
4 x 1020
187Pb
1 x 107 34
Options to be explored: Deceleration, Multi-charge state operation (increase luminosity) ?

39. Feasibility Study
Elastic proton scattering 132Sn (Matter Distribution)
Inelastic alpha scattering on Sn isotopes (Giant Monopole Resonance)
Skin and haloes in heavy neutron-rich
nuclei, nuclear potential parameters
Collective modes in asymmetric
nuclei, nuclear matter compressibility
counts per hour
High sensitivity of the method
(simulation of experimental conditions
as expected at the NESR with a
luminosity of 1028 cm-2 s-1)

40. Time Schedule
First experiments scheduled for beginning of 2012 (Super-FRS) – Phase I
End of project scheduled for beginning of 2015
Schedule determined by civil construction progress (start of CC early 2007)

41. FAIR – Facility for Antiproton and Ion Research in 2015
First experiments at Super-FRS in early 2012
Thank you
Austria China Finnland France Germany Greece India Italy Poland Spain Sweden Russia Great Britain Romania

42. Conclusions
 investigations of direct reactions at low q are of high interest
 the active target performance at R3B is complemantary to that of EXL
(short lifetimes, small beam intensities)
 for these conditions the active target setup will provide sufficient luminosities
 the requirements are different to those of low energy experiments
(large volume, large dynamic range)
 still some questions to be solved:
- requirements for other reactions
- magnetic field or high pressure ?
- shielding of the large emittance beam (2cm)

44. Required Angular Resolution

45. The IKAR Collaboration

46. Expected Luminosities  Full Simulation of Production, Transport and Storage
Inelastic ( e.g. GR studies )
Quasielastic (spectroscopic factors)
charge distributions
charge radii
For too unstable nuclei (T1/2< 1d)
accessible for the first time !
890
Isotopes
1472

47. Scope of Project: FAIR Baseline Technical Report
Approved by ISC in May 2006

48. VI. Nuclear Physics with Radioactive Beams at FAIR
Superconducting FRagment Separator
High-Energy Reaction Setup
Multi-Storage Rings (CR, NESR, eA)
Energy-Bunched Stopped Beams
Three Experimental Areas
Key characteristics : all elements, H to U intensity > 1012 ions/sec high and low energies pulsed and CW beams

49. RIB‘s from the Super-FRS
II.3. Feasibility Studies and R&D for the NUSTAR Project EXL EXL: EXotic Nuclei Studied in Light-Ion Induced Reactions at the NESR Storage Ring
Electron
cooler
eA-Collider
RIB‘s from the Super-FRS
EXL
ELISe
R&D on
 UHV capable Si and Si(Li) Detectors  Calorimeter design  Vacuum and target technology
Design goals:
 Universality: applicable to a wide class of reactions  High energy and angular resolution  Specially dedicated for low q measurements with high luminosity (> 1028 cm-2 s-1)

50. Production of Radioactive Beams at Relativistic Energies
( ) MeV/u

51. Proposed Experiments at FAIR
 investigation of nuclear matter distributions along isotopic chains towards proton/neutron asymmetric matter
 investigation of the same nuclei by (e,e) (ELISe) and (p,p) (EXL) scattering  separate neutron/proton content of nuclear matter  unambiguous and “model independent” determination of size and radial shape of neutron skins (halos)
theoretical prediction: P.-G. Reinhard
example: Sn isotopes at the nuclear surface: almost pure neutron matter  probe isospin dependence of effective in-medium interactions  sensitivity to the asymmetry energy (volume and surface term!)

52. I. Introduction
The radial shape and size of nuclei is a basic nuclear property !
 of high interest for nuclear structure and astrophysics
<r2>1/2
(r)
observables:
nuclear charge distribution: ch(r), <rch2>1/2  leptonic probes
nuclear matter distribution: m(r), <rm2>1/2  hadronic probes
standard methods: (see also C.J. Batty et al., Adv. in Nucl. Phys. 19 (1989) 1-188)
nuclear charge distribution: electron scattering
isotope shifts
muonic atoms
nuclear matter distribution: (p,p), (α,α), (π,π), ....

53. VI. Nuclear Physics with Radioactive Beams at FAIR
Superconducting FRagment Separator
High-Energy Reaction Setup
Multi-Storage Rings (CR, NESR, eA)
Energy-Bunched Stopped Beams
Three Experimental Areas
Key characteristics : all elements, H to U intensity > 1012 ions/sec high and low energies pulsed and CW beams

54. V. Conclusions
d nuclear physics with at the present GSI facility: many results on nuclear structure - nuclear astrophysics
T the future facility FAIR will allow to reach unexplored regions in the chart of nuclei, where new and exciting phenomena are expected.
T the EXL,R3B and ELISe setups are designed as universal detection systems providing high resolution and large solid angle coverage for kinematically complete measurements.
t the use of stored cooled radioactive beams will have considerable advantage over external target experiments for measurements at low momentum transfer. 

55. I. Introduction classical method of nuclear spectroscopy:
 light ion induced direct reactions: (p,p), (p,p'), (d,p), ...  to investigate exotic nuclei: inverse kinematics
proton-detector
beam of exotic
nuclei AX
1H (AX, 1H) AX
1H - target
past and present experiments:
 light neutron-rich nuclei: skin, halo structures  only at external targets  new technologies: active targets LH2 target
future perspectives at FAIR:
 explore new regions of the chart of nuclides and new phenomena  use new and powerful methods:
EXL: direct reactions at internal NESR target  high luminosity even for very low momentum transfer measurements

56. Investigation of Nuclear Matter Density Distributions of Halo Nuclei by Elastic Proton Scattering at Low Momentum Transfer
nuclear matter
distributions:
nucleus
Rn*, fm
Rn-Rp*, fm
Rhalo, fm --
3.08 (10)
2.59 (9)
0.48 (9)
11Li
4.06 (23)
1.73 (23)
6.54 (38)
 *with charge radius from laser spectroscopy (R. Sanchez et al.)  neutron radius and neutron skin (halo) determined
nuclear matter
radii:
nucleus
Rmatter, fm
Rcore, fm
Rhalo, fm
4He
1.49 (3) --
8He
2.45 (7)
1.55 (15)
3.08 (10)
9Li
2.43 (7)
11Li
3.62 (19)
2.55 (12)
6.54 (38)
 extended neutron distribution in 8He and 11Li obtained
 size of core, halo and total matter distribution determined with high accuracy

57. II. Intermediate Energy Elastic Proton Scattering
- a Tool to Study the Radial Shape of Exotic Nuclei
The radial shape and size of nuclei is a basic nuclear property !
 of high interest for nuclear structure physics
(r)
<r2>1/2
observables: nuclear charge distribution: ch(r), <rch2>1/2  leptonic probes
nuclear matter distribution: m(r), <rm2>1/2  hadronic probes
method: intermediate energy elastic proton scattering
 well established method for determination of nuclear matter distributions (of stable nuclei)
 what about exotic nuclei?

58. Sensitivity of Elastic Proton Scattering on the Radial Shape of the Nuclear Matter Distribution
slope of d/dt  matter radius Rm
curvature of log (d/dt)  halo structure

59. Elastic Proton Scattering at Low and Intermediate Energies
for intermediate energy proton scattering (Ep  700 – 1000 MeV):
reaction mechanism and effective nucleon-nucleon interaction well defined
 Matter distribution (r) related to differential cross sections
in straight forward way (Glauber theory)
for low energy proton scattering (Ep = 20 – 100 MeV):
quantitative determination of (r) limited by:
 potential ambiguities
 uncertainties in effective pp, pn interaction

60. Light-Ion Induced Direct Reactions
elastic scattering (p,p), (,), … nuclear matter distribution (r), skins, halo structures
inelastic scattering (p,p’), (,’), … deformation parameters, B(E2) values, transition densities, giant resonances
charge exchange reactions (p,n), (3He,t), (d, 2He), … Gamow-Teller strength
transfer reactions (p,d), (p,t), (p, 3He), (d,p), … single particle structure, spectroscopic factors spectroscopy beyond the driplines neutron pair correlations neutron (proton) capture cross sections
knock-out reactions (p,2p), (p,pn), (p,p 4He)… ground state configurations, nucleon momentum distributions, cluster correlations

61. Advantage of Storage Rings for Direct Reactions in Inverse Kinematics
 high resolution due to: beam cooling, thin target (1014/cm2)
 gain of luminosity due to: continuous beam accumulation and recirculation
 low background due to: pure, windowless 1,2H2, 3,4He, etc. targets
 separation of isomeric states

62. The EXL Recoil and Gamma Array
Si DSSD  E, x, y
300 µm thick, spatial resolution better than 500 µm in x and y, ∆E = 30 keV (FWHM) 􀂾
Thin Si DSSD  tracking
<100 µm thick, spatial resolution better than 100 µm in x and y, ∆E = 30 keV (FWHM)
Si(Li)  E
9 mm thick, large area 100 x 100 mm2, ∆E = 50 keV (FWHM)
CsI crystals  E, 
High efficiency, high resolution, 20 cm thick

63. The IKAR-Collaboration
F. Aksouh, G.D. Alkhazov, M.N. Andronenko, L. Chulkov, A.V. Dobrovolsky, P. Egelhof, H. Geissel, M. Gorska, S. Ilieva, A. Inglessi, A.V. Khanzadeev, O. Kiselev, G.A. Korolev, C. L. Le, Y. Litvinov, G. Münzenberg, M. Mutterer, S.R. Neumaier, C. Nociforo, C. Scheidenberger, L. Sergeev, D.M. Seliverstov, H. Simon, N.A. Timofeev, A.A. Vorobyov, V. Volkov, H. Weick, V.I. Yatsoura, A. Zhdanov
Gesellschaft für Schwerionenforschung, Darmstadt, Germany
Petersburg Nuclear Physics Institute, Gatchina, Russia
 Kurchatov Institute, Moscow, Russia
Institut für Kernchemie, Universität Mainz, Germany Institut für Kernphysik, TU Darmstadt, Darmstadt, Germany

65. The Ring Branch Experiments: Mass- and Lifetime Measurements
Electron and p Scattering off Exotic Nuclei
Nuclear Reactions at Internal Targets

66. External Target Versus Internal Target
Luminosity
EXL
R3B
(106 pps)
( for 1.5 mrad resolution ) 1 10
100
1E-4
1E-3
0.01
0.1
1E22
1E23
1E24
1E25
1E26
1E27
1E28
132Sn..
EXL
+ R3B
EXL only
104Sn.. CH
target 2
liH
target 2
LH2 2
134Sn..
CH2
Max. external target thickness
, mg/cm
Quasifree r
Elastic scatt.
Giant Resonances
Spin-isospin excitation
Ep, MeV

67. Increase of Dynamic Range with Magnetic Field

68. III. Very Recent Results on Elastic Proton Scattering from Exotic Nuclei
 two experiments with primary 12C and 18O beams were successfully performed
 data on 7Be, 10Be, 11Be, 12Be, 14Be and 8B were taken: S.Ilieva, A. Inglessi et al.
one-neutron halo
6He
8He
11Be
14Be
17B
19C
11Li O N C B Be Li He H
proton halo
two-neutron halo
four-neutron halo 8B
19B
22C
candidates for halo nuclei

69. Concept of the Data Analysis
·  Glauber multiple-scattering theory for calculation of cross sections:
– use measured free pp, pn-cross sections as input (in medium effects negligible) – fold with nucleon density distribution
– take into account multiple scattering (all terms!) (small for region of nuclear halo!)
·   variation of the nucleon density distribution:
a) phenomenological parametrizations (point matter densities):
G: 1 Gaussian
SF: Symmetrized Fermi
GG: 2 Gaussians
GO: Gaussian + Harmonic Oscillator
b) “model independent” analysis:
SOG: Sum Of Gaussians (standard method for electron scattering data: I. Sick, Nucl. Phys. A 218 (1974) 509)