A High Rigidity Spectrometer for FRIB

Remco Zegers for the HRS working group

HRS whitepaper – 2014

1st FRIB-China Workshop on Physics of Nuclei and HadronsMay 28-30, 2015

https://www.phy.anl.gov/nsac-lrp/Whitepapers/HRS%20white%20paper.pdf

2

Whitepaper contributors & Users

Argonne National Laboratory Hope College Texas A&M University

Augustana College Indiana UniversityUniversity of Notre Dame

Bucknell University Kalamazoo College University of TennesseeCentral Michigan University

Lawrence Berkeley National Laboratory

University of Washington

Florida State UniversityLos Alamos National Laboratory Ursinus College

Gettysburg CollegeMichigan State University Wabash College

Hampton University Ohio University Westmont College

Users from the following US institutions contributed to the white paper

In addition, researchers from institutions in Canada (TRIUMF), Europe (GSI and FAIR) and Japan (RIBF, RIKEN) and their users, were involved and contributed to the whitepaper.

Based on the experiences with the S800/Sweeper and the size of the FRIB users community, a user community of over 500 scientists for the HRS is expected

3

Endorsements2014 Town MeetingsIn the resolution of the 2014 APS Division of Nuclear Physics Town Meeting on Nuclear Structure, timely construction of the HRS as a state-of-the-art instrument for FRIB was recommended. In the resolution of the 2014 APS Division of Nuclear Physics Town Meeting on Nuclear Astrophysics, the HRS was listed as a critical piece of equipment, and the development and implementation was recommended.

The FRIB Scientific Advisory Committee (SAC) has continuously endorsed the scientific need for the HRS in its assessments of the plans presented by the HRS Working Group: “The SAC viewed the science addressed in your submission as having the highest scientific priority and this was communicated to the FRIB Laboratory Director…The SAC views the activity of your group as central to the FRIB mission and encourages your continued actions…The HRS is one of the flagship projects at FRIB. To facilitate the fast beam programs, the HRS is designed to be coupled with detectors necessary for experiments enabling techniques such as missing-mass, in-beam gamma and invariant mass in inverse reactions…The HRS is necessary to conduct the scientific mission of FRIB.”

Spectrometers for fast beams at NSCL

The magnetic rigidity of the S800 and Sweeper are limited to ~4 Tm.

5

Ancillary detectors used at S800 & Sweeper enable a very diverse scientific program

SeGA CAESAR

GRETINA

PLUNGER

HiRA

LENDA

LH2/LD2 target

Diamond Tracking

About half of all NSCL experiments are with S800 spectrograph or Sweeper

6

Optimizing the scientific opportunities at FRIBFRIB will produce the most exotic isotopes at

unprecedented intensities by fast fragmentation of heavy-ion beamsTo minimize losses, experiments with the most exotic species are best performed at the energy at which maximum production rate is achievedAvailable spectrometers at NSCL lack necessary bending power – the proposed HRS overcomes this serious limitation

7

The magnetic rigidity (B) required for achieving the maximum rare-isotope beam intensity is larger than 4 Tm for almost all species produced at FRIB, and ranges up to 8 Tm for the most neutron-rich species

S800 and sweeper spectrometers currently available at NSCL have bending limits of 4 Tm

The High Rigidity Spectrometer at FRIB

8

The gains are strongest for the most neutron-rich systems.

Luminosity gains are more than a factor of 10 for neutron-rich isotopes: same effect as having 4000 kW primary beam power instead of 400 kW

Tremendous increase of the discovery potential of FRIB, including at early operations when beam power is not yet maximal

The HRS will increase the luminosity for experiments with fast rare-isotope beams for the vast majority of nuclei available at

FRIB

9

Luminosities at the HRS1) The rare-isotope beam delivery rate to the experimental station is up to 5 times higher when beams are produced at the optimal beam energy compared to the rate when slowed down to match currently available rigidities at NSCL. The gains are highest for the most neutron-rich species.

4 4.5 5 5.5 6 6.5 7 7.5 80

200

400

600

800

1000

1200

1400

Rigidity (Tm)

Targ

et

thic

knes

(mg/c

m2)

2) Luminosities at optimum rigidity are further increased by significant factors because thick reaction targets can be used

60Ca on 9Be for fixed d of 5% to ensure energy resolutions ~ 2% (FWHM) for experiments with GRETA@HRS

optimum rigidityfor production

x4 luminosity

10

3) At higher beam energies, charge-state production is reduced, increasing yields and simplifying experiments; Most important for experiments with heavier nuclei

Luminosities at the HRS

Luminosity gains with the HRS exceed a factor of 10 for experiments with neutron-rich rare isotopes for which the potential for scientific discovery is highest

11

No Program

1 Study of Shell Structure

2 Superheavy Elements

3 Neutron Skins

4 Pairing

5 Nuclear Symmetries

6 Equation of State

7 r-process

8 15O(α,γ)

9 59Fe s-process

10 Medical Isotopes

11 Stewardship

12 Atomic EDM

13 Limits of Stability

14 Halo Nuclei

15 Mass Surface

16 rp-process

17 Weak Interactions

Scientific program of the HRS:

• Is responsive to 12 of 17 NSAC RIB Task Force benchmarks

• Covers all four overarching questions of the NRC decadal study• How did visible matter come into

being and how does it evolve?• How does subatomic matter organize

itself and what phenomena emerge?• Are the fundamental interactions that

are basic to the structure of matter fully understood?

• How can the knowledge and technological progress provided by nuclear physics best be used to benefit society?

Evolution of nuclear structureStudy the modification of the nuclear potential, the impact of the nucleon-nucleon interaction on single-particle energies and increased many-body correlations far some stability to generate a complete description of nuclei, with applications in stewardship science and astrophysics

Tools: • invariant mass spectroscopy (at the dripline)• in-beam -ray spectroscopy with intermediate-energy

Coulomb excitation• inelastic proton scattering and nucleon removal reactions• inelastic and charge-exchange reactions• recoil-distance Doppler-shift measurements• isomer and fission studies• commensal decay spectroscopy• …

S. Suchyta et al., PRC89, 021301(R) (2014)

Gretina-detection

S800 Spectrograph+Gretinafirst campaign 2012-2013

Gamma-Ray Energy Tracking In-beam Nuclear Array

S800 Spectrograp

h

Highly successful science campaign with 24 experiments

14

Proposed by the GRETINA/GRETA community• Efficiency (~40% at 1 MeV)

• 4π Coverage: Angular distributions/correlations. High-energy efficiency by proper summing of scattered γ-rays, no solid angle lost to Compton shields

• Position resolution (σx,y,z = 2 mm) Position of 1st interaction Excellent Doppler reconstruction, in-beam energy resolution

• Excellent peak-to-background ratio

Tracking Reject partial-energy events, maintaining good spectral quality

https://www.phy.anl.gov/nsac-lrp/Whitepapers/GRETA_WP_LE_TM_Full.pdf

15

Understanding the nuclear force – Changes in the nuclear shell structure

•The neutron-rich Ca isotopes beyond 48Ca provide textbook examples of shell evolution

•Microscopic calculations suggest a sensitivity of the detailed structure to the inclusion of a variety of many-body correlations, including 3N forces

GRETA@HRS(simulated)

9Be(61Sc,60Ca+)50Ca -> 49Ca GRETINA @ NSCLGEANT4 simulation

57Ca -> 56Ca

γ-γ

• Detailed studies of single particle structure, provide a critical test of effective interactions and 3N forces

• The structure around 60Ca informs the location of the drip line at Z = 20GRETA@HRS will have superior sensitivity for fast-beam

experiments compared to any other γ-ray detector

16

Nuclear structure beyond the neutron drip line – Invariant mass spectroscopy

•Highly successful program at NSCL will be extended along the neutron drip line to heavier systems: excellent discovery potential for:

•Evolution of shell-structure away from stability; the discovery of new magic numbers

•New phenomena, such as the recently discovered two-neutron radioactivity of 26O

•Decay properties reveal many-body correlations in nuclei and connect to open quantum systems

Layout of HRS is optimized to detect neutrons at forward angles for invariant mass spectroscopy

Nuclear Astrophysics

Nuclear Astrophysics: understand the nuclear reactions and processes that drive stellar evolution and nucleosynthesis, provide the nuclear physics input to interpret astronomical observation with complete simulations of astrophysical phenomena and objects

Some of the experimental tools available at HRS• Heavy-ion collisions and projectile multifragmentation• charge-exchange reactions/weak reactions• proton and alpha decay branching ratios measurements• time-of-flight mass measurements• invariant-mass spectroscopy• …

SN 1994D ESA/Hubble

Müller, E. and Janka, H.-T.A&A 317, 140–163, (1997)

18

Time-of-flight mass measurements reaching the r-process

• Masses can be deduced from the simultaneous measurement of an ion's time-of-flight, charge, and magnetic rigidity thorough a magnetic system of a known flight path

• With the HRS at FRIB, this will approach can reach a large fraction of the r process nuclei up to N=100 and comes close to the r-process path beyond

• Masses are crucial for modeling the r process and so finally unraveling its site• 65m flight path to the end of the HRS, ~400ns flight time at FRIB energies and anticipated TOF and position detector resolutions allow for 0.2 MeV precision for masses around N=100

19

Weak reaction rate for nuclear astrophysics• Supernovae are considered as major sources of nucleosynthesis and their

shockwaves drive galactic chemical evolution• Understanding the evolution of core-collapse and thermonuclear

supernovae, as well as crustal processes in neutron stars requires an accurate knowledge of reaction rates mediated via the weak force (e-capture/-decay/neutrino-induced) on medium-heavy nuclei

• Charge-exchange reactions at intermediate energies in are the best way to measure relevant weak-interaction strengths distributions and benchmark theoretical models

• Inverse kinematics (104pps needed)– (7Li,7Be+γ) – HRS+GRETA– (d,2He) – HRS and Active Target TPC– (p,n) – HRS+LENDA

Recent result with LENDA@S80056Ni(p,n) in inverse kinematics

20

Scope1.A high-rigidity, large-acceptance beam line to transport the rare isotopes

with minimal losses from the FRIB fragment separator to the HRS spectrometer

2.A sweeper dipole behind the reaction target for diverting charged particles3.A focusing beam line that transports the diverted particles from the sweeper

dipole to two spectrometer dipoles for analysis4.Two spectrometer dipoles for identifying and analyzing charged particles5.Charge-particle detectors that are i) placed in the beam lines for tracking

rare-isotopes that are impinged on the reaction target, and ii) placed in the focusing beam line and final focal plane to analyze the particles emerging from reactions in the target

6.Civil infrastructure to house the HRS

1 2

3

4

5

6

21

High Rigidity SpectrometerPre-conceptual (first order) ion-optical design

SpectrometerMagnetic bending power: up to 8 TmLarge momentum (10% dp/p) and angular acceptances (80x80 mrad)Particle identification capabilities extending to heavy masses (~200)Momentum resolution 1 in 5000; intermediate image after sweeperDispersion: 7cm/%Invariant mass spectroscopy: 6o opening in sweeper dipole for neutrons

Beam transportDispersion-matching capabilityBeam line from fragment separator designed to optimize transmission to HRS

Zmin= 43.00 m Zmax= 70.00 m Xmax= 50.0 cm Ymax= 50.0 cm Ap * 1.00 Thu Jun 05 11:32:33 2014

D1

20.941

D1

20.941

2QA

19.000

2QB

-28.646

2QC

24.169

3QA

11.472

3QB

-26.334

3QC

17.032

-20.941

-20.941

F0

D1F

F1

S1

S2

F2

D2

F3

F4

F5

F6

F7

F8

'HRS Preconcept May 2014 #25'

22

HRS Project Notional Budget

Equipment Labor Total* Including contingency

Beam line $3.9M $4.8M $8.7M $11.4M

HRS $4.1M $8.3M $12.4M $17.8M

Total $8.0M $13.1M $21.1M $29.1M

*Excludes civil infrastructure

Because of the high impact on the FRIB science program, completion of the HRS by ~2024 is envisioned

23

Summary• The fast-beam program with the High Rigidity

Spectrometer (HRS) will optimize the discovery potential of FRIB by enabling experiments at the highest intensities with the most neutron-rich isotopes. Gain factors in luminosity of factors of 10 or more can be achieved, with the largest gains for the most exotic species.

• The HRS will increase the scientific reach from other state-of-the-art and community-priority devices, such as the Gamma-Ray Energy Tracking Array (GRETA) and the Modular Neutron Array (MoNA-LISA), in addition to other ancillary detectors.

• There are many opportunities to collaborate on the HRS and the associated science program, and this is a good time to consider such opportunities.