# Presentation: 656466

## Exotic Beam Production and Facilities II

**Brad Sherrill**, *Michigan State University*
- _Lecture I_
- The Rare Isotope Accelerator Concept
- Some history and background
- The status of exotic beam plans in the USA
- _Lecture II_
- Methods of exotic beam production
- Production mechanisms (e.g. fragmentation)
- Current world situation for exotic beams

## Production Mechanisms

- _In-flight Separation_
- _ISOL – Isotope Separation On-Line_
- _Neutron induced fission (2-step target)_

- Post Acceleration

- Driver Accelerator

- Fragment Separator

- beam

- Gas cell catcher/ion source

- Driver

- Neutrons

- Post Acceleration

- Post Acceleration

- Beams used without stopping

## Advantages/Disadvantages of ISOL/In-Flight

- Small beam energy spread for fusion studies
- Can use chemistry (or atomic physics) to limit the elements released
- 2-step targets provide a path to MW targets
- High beam intensity leads to 100x gain in secondary ions

**Advantages/Disadvantages of ISOL/In-Flight**

- Provides beams with energy near that of the primary beam
- For experiments that use high energy reaction mechanisms
- Luminosity (intensity x target thickness) gain of 10,000
- Individual ions can be identified
- Efficient, Fast (100 ns), chemically independent separation
- Production target is relatively simple

_**In-flight:**_
**GSI**
**RIKEN**
**NSCL**
**GANIL**

_**ISOL:**_
**HRIBF**
**ISAC**
**SPIRAL**
**ISOLDE**

- 400kW protons at 1 GeV is 2.4x1015 protons/s

## Production Methods – Low Energy

- Ep < 50 MeV
- Used for the production of medical isotopes.
- Selective, large production cross sections (100 mb), and intense (500 A) primary beams.
- Used at HRIBF(ISOL), LLN (ISOL), ANL (in-flight) and Notre Dame (in-flight), Texas A&M (in-flight)
-  Fusion
- Low energy 5-15 MeV/A and “thin” targets
- Selective with fairly large production cross sections.
- Used at ANL(in-flight), JYFL (Jyväskylä)

**Production Methods – Low Energy**

## Example of production by fusion

-  Example: 58Ni(3He,n)60Zn, EHe = 100 MeV
- Production cross section from ALICE:  100 b
- 4 g/cm2 target
- Yield of 60Zn is 3x107/pA (LBL 88-inch has 10 pA of 3He)
- Heavier beams can have larger cross sections, but require thinner targets.

**Example of production by fusion**

## Low Energy - Continued

- Significant cross section between 10 - 50 MeV/A (this energy range implies thin targets, mg/cm2)
- High production of nuclei near stability.
- Multi-nucleon reactions can be used to produce rare or more neutron rich nuclei, e.g. GSI mass separator had a program to study neutron rich f-p shell nuclei using neutron transfer.
- Deeply inelastic reactions
- Deep inelastic - much of the KE of the beam is deposited in the target.
- Was used to first produce many of the light neutron rich nuclei
- Is used to study neutron rich nuclei since the products are “cooler” and fewer neutrons are evaporated than in fusion reactions.

**Low Energy - Continued**

## Production Mechanisms – High Energy

- Projectile fragmentation of high energy (>50 MeV/A) heavy ions
- Target fragmentation of a target with high energy protons or light HIs. In the heavy ion reaction mechanism community these are called *intermediate mass fragments*.
-  Spallation (ISOLDE, TRIUMF-ISAC)
- Name comes from spalling or cracking-off of target pieces.
- One of the major ISOLDE mechanisms, e.g. 11Li made from spallation of Uranium.
-  Fission (technically not only high energy)
- There is a variety of ways to induce fission (photons, protons, neutrons (thermal, low, high energy)
- The fissioning nuclei can be the target (HRIBF) or the beam (GSI/MSU/RIKEN).
-  Coulomb Breakup
- At beam velocities of 1 GeV/n the equivalent photon flux as an ion passes a target is so high the GDR excitation cross section is many barns.

**Production Mechanisms – High Energy**

## Fission Cross Sections

**Fission Cross Sections**

- Low energy fission can lead to higher yields for certain nuclides.
- This is the basis of the electron driver upgrade of the HRIBF.

## HRIBF eBeam Upgrade

- Bremsstrahlung from the electron beam induces photo-fission in a uranium carbide target system with a thickness of ~35 g/cm2
- A 50 kW, 100 MeV electron beam incident on such a target would generate a total uranium fission rate 25 times greater than a 20 μA, 50 MeV proton beam.
- In addition, the yield of neutron-rich species is shifted much farther from stability than for proton induced fission.
- This would result in a factor of 1,000 to 10,000 increase in beam intensities at HRIBF

- http://www.phy.ornl.gov/hribf/initiatives/electrons/

## Terminology for High Energy Reactions

- Projectile
-  Fragment

- Spallation
- Product

- Intermediate Mass Fragment/ Target Fragment

**Terminology for High Energy Reactions**

- The fragment could emit nucleons (fragmentation) and/or fission

- See the lectures of D Bazin

- ABRABLA - A. R. Junghans, K.-H. Schmidt et al, Nucl. Phys. A 629 (1998) 635

## Overview of the In-Flight Technique

**Overview of the In-Flight Technique**

- Wedge location
- D = 5 cm/%
- R = 2500 p/p

- 100 pnA 86Kr
- 5 kW Beam power

- 8 msr
- p = 5%

- Example: The NSCL Coupled Cyclotron Facility

- 65% of the 78Ni is transmitted

- Morrissey and Sherrill: Euroschool Lectures

## Multiple stages of separation

- H. Geissel et al. NIM B

- Higher energy provides cleaner separation.

## LISE++ Simulation Code

- The code operates under Windows and provides a highly user-friendly interface. It can be downloaded freely from the following internet address:
-       http://www.nscl.msu.edu/lise

- O. Tarasov *et al.*

## Facility Specifications

**Facility Specifications**

- 78Ni from 86Kr
- No secondary reactions

- Tony Nettleton

## Fragmentation at 400MeV/u

**Fragmentation at 400MeV/u**

-  Angles ≤ ± 20 mrad
-  Momentum ± 3 - 8 %

- Relatively ‘easy’ due to small phase space

- Momentum distrib.

- 100Sn

- 200W

- M. Hausmann, T. Nettleton

**Notes:**
So what is the fragment beam we’ll have to deal with? Here 2 examples for fragmentation, for both shown the angular distribution of the fragments after the target and momentum distributions. The message is that these are reasonably manageable.

## In-Flight Fission at 400 MeV/u

**In-Flight Fission at 400 MeV/u**

- Angles ± 40 - 60 mrad
-  Rigidity ± 6 - 10 %
-  Plus correlations due to fission kinematics

- More challenging due to larger phase space

- 132Sn

- 76Ni

- M. Hausmann, T. Nettleton

**Notes:**
More challenging: fission due to the kinematics of the fission process; also two examples, one heavy with angles up to +/- 40 mrad, one light with even larger angles + broad momentum distribution.

## NSCL Coupled Cyclotron Project

- Experimental Areas

- Cyclotrons – up to MeV/u

- ECR

- Operational – will study N=82 nuclei and nuclei along the neutron drip line up to mass 30.

## Particle Identification

## Beams Produced with CCF/A1900

**Beams Produced with CCF/A1900**

**Notes:**
In the past 12 months (5/1/2002 to 4/30/03), there were 25 primary beam tunes, involving 9 beam species, distributed as follows:

16O at 150 MeV/nucleon... 3 times....312 hrs
36Ar at 150 MeV/nucleon...7 times...790 hrs
40Ar at 140.......................3 times...210 hrs
48Ca at 110.......................1 time...192 hrs
58Ni at 140.......................2 times...476 hrs
76Ge at 130.......................2 times...209 hrs
86Kr at 140.......................3 times...859 hrs
124Xe at 140......................2 times...407 hrs
136Xe at 120.....................2 times..338 hrs
Total of 3793 hours

## GSI Current RNB Facility

-  Production of 100Sn and 78Ni
-  Hundreds of new masses and isotopes, ...

## Cold Fragmentation Studied at GSI

- 197Au + Be at 950 *A *MeV

- J. Benlliure, K.-H. Schmidt, et al. Nuclear Physics A 660 (1999) 87

- 5

## The GSI FAIR Facility Layout

- from J. Nolen ANL

## RIKEN Radioactive Ion Beam Factory

**RIKEN Radioactive Ion Beam Factory**

- from J. Nolen ANL

## RIKEN RIBF Heavy-ion accelerator system

- An ion source current of 32 p-μamps is required to reach uranium beam goal.

**Notes:**
須田さんより。

## Targets and Production Mechanisms

- from J. Nolen ANL

## Production is only one part of the equation

- H. Ravn

-  - production cross section
- Ib - beam intensity
- Tuseable - usable target thickness
- diff – diffusion efficiency
- des – desorption efficiency
- eff – effusion efficiency
- is_eff - ionization efficiency
- accel_eff - acceleration efficiency

**Production is only one part of the equation**

- target

## ISOLDE

**http://isolde.web.cern.ch/ISOLDE/**

- CERN
- PSB
- 1 GeV protons
- 2 mA
- Intensities up to 1011 pps

- Accelerate to 3.0 MeV/u

## SPIRAL at GANIL

- http://www.ganil.fr/spiral/index.html

## GANIL SPIRAL-2

- Completion
- ~2011

## ISAC Radioactive Beam Facility - ISOL

- Beams are produced by 500 MeV protons from TRIUMF cyclotron.

- 2x109 22Na/s

- ISAC-II underway

## ISAC-2 overview

- ISAC has a fixed 500-MeV proton beam driver with 50-kW power.

## Texas A&M Upgrade Project

- http://cyclotron.tamu.edu/

- Radioactive beams to 50 MeV/u
- Difficult isotopes from the ion-guide

## EURISOL

- 5 MW Proton LINAC

- http://www.ganil.fr/eurisol/index.html

## Overview of the RIA Concept

## Forces in gas catcher system

- A combination of forces working together is required to obtain
- Fast extraction times over the full volume
- High efficiency over the full volume
- Tolerance to high intensity

**Forces in gas catcher system**

- from J. Nolen ANL

## Momentum Compensation

- Diagram: H. Weick et al., NIM B 164-165 (2000) 168

- FWHM = 32 atm-m 4He

- FWHM = 0.93 atm-m 4He

- Above: Range compression of 350 Mev/u 130Cd produced from 500 MeV/u 136Xe
- (MOCADI simulation)

- 130Cd

- M. Amthor

**Notes:**
Rate must be held to no more than 10^9 pps for entry into gas cell

## Gas Stopping in use at the NSCL

**beam ****from **
**A1900**

**9.4 T Penning**
**trap system**

**mass measurements**

_**Many systematic studies:**__** **_**L. Weissman et al., NIM A522 (2004) 212, NIM A531 (2004) 416, Nucl. Phys. A746 (2004) 655c, NIM  A540 (2005) 245.**

- LEBIT project

**92 MeV/U ****38****Ca/****37****K**

- Degrader thickness m

- efficiency

**Gas Stopping in use at the NSCL**

## RIA prototype gas catcher tested at GSI

**GSI experiment S258**
**Savard(ANL), Scheidenberger (GSI) *****et al.***

- Bragg peak from 56Ni beam
- Bragg peak from 54Co beam
- Bragg peak from 52Fe beam

- 54Co

- 52Fe

**~ 50 % of radioactive ions stopped in the gas catcher were extracted as a radioactive ion beam!**

**ANL**, GSI, KUL, MSU, RIKEN, ...

**RIA prototype gas catcher tested at GSI**

## ANL Upgrade based on 252Cf Fission

- Guy Savard, ANL

## ANL ATLAS upgrade: CARIBU

## Yields from the ANL Upgrade

- Guy Savard, ANL

## SRIM & PIC calculation by M.Facina

**Stopping volume ******** 75 cm****3**
**Ionization ******** 1.7 x 10****6**** IP/ion**

- He+ created by a 100 pps 38Ca beam in 760 Torr

## Cyclotron Gas Stopper Concept

**Cyclotron Gas Stopper Concept**

**Gas-filled weakly-focusing cyclotron magnet w/ RF guiding techniques at end-of-range **

**Low gas pressure **
**	******** ****long stopping path **
**	******** ****fast drift & extraction**
**Separate He****+**** from rare ions **
**	******** ****minimal space-charge**** **

**Exotic atom studies in a cyclotron trap for antiprotons, pions, and muons ****	**L.M. Simons, Hyperfine Interactions 81 (1993) 253
**Proposal for a cyclotron ion guide with RF carpet ****	**I. Katayama, M. Wada, Hyperfine Interactions 115 (1998) 165
**A Study of Gas-Stopping of Intense Energetic Rare Isotope Beams ****	**G. Bollen, D.J. Morrissey, S. Schwarz, NIM A550 (2005) 27

**Features/Expectations:**

## Initial Stopping Calculations

**100 MeV/A Br [ 2.6 mm Al ]******** 610 MeV Br ****Field B****max**** = 2 T, n = 0.2**

- 10 mbar He

**Beam simulations of ions in gas-filled weak-focusing magnet by Bollen**

**High space-charge and stopped-ion regions are separated !   **
**Intensity limits > 10****8****/s**

**Energy loss or Ionization density**

**Stopped-ion distribution lies inside dashed circle**

- Top view

## NSCL Stopping Cyclotron (Under Design)

- Superconducting magnet system Bmax = 2 T, n = 0.2, rinj = 0.7 m

- High Energy
- Beam

- D.Lawton, A.Zeller (NSCL)

## Beam Simulation including Injection

**One Trajectory in ‘real’ field**

**Energy vs. Position**

- degrader

**100 MeV/A ****79****Br on 2.6mm Al ******** 610 MeV ****78****Br**

- F. Marti (NSCL)

## Minimizing extraction time

- Simulations of ion motion on RF carpets in 2 Tesla field

**Low gas pressure (10 mbar compared to 200 - 1000 mbar in present systems)  **
**Time for collection onto carpet and transport out of gas stopper < 5 ms !**

- RF 400V; 1.5MHz
- DC gradient 20V/cm
- Spacing 1 mm, 0.5 mm thick

## NSCL Reacceleration Stage Options

- Reaccelerated beam area

- Stage I: 3 MeV/u

- Stage II:  12 MeV/u

## You ask: Should I switch fields?

- Construction of a 1 B$ facility in the US in the next 5 years is unlikely
- There are positive signs (3rd on the DOE list of facility priorities; congressional mandate of RIA; highest NSAC priority) that something on the scale of 600 M$ will happen
- This is a very active field world-wide
- NSCL, TRIUMF, HRIBF, ANL, T A&M, etc.
- Upgrades at NSCL, ANL, HRIBF
- Large scale international facilities: FAIR, RIBF, SPRIRAL II, EURISOL, ...
- There are exciting, important questions to answer

## Additional Material

## RIA White Papers

- One of the best places to find out more information regarding RIA is the RIA users web site.
- _Overall info:_
- http://www.orau.org/ria/
- _White papers:_
- http://www.orau.org/ria/pubs.htm

## Universality of Production Cross Sections

**Universality of Production Cross Sections**

- Na isotopes

## Limiting Fragmentation

- The production yield of residues saturates with a total beam energy of a few GeV. **Limiting Fragmentaton**
- H. Ravn - “The saturation cross-section for more exotic species may well first be reached beyond 5 GeV.”

- Kaufman and Steinberg, PRC 22 (80) 167.

**Limiting Fragmentation**

## Limiting Fragmentation continues to high energy

- Moretto and Wozniak, Ann. Rev. 45 (93)

- p + Xe
- at 48.5 degrees

**Limiting Fragmentation continues to high energy**