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Rare Isotope AcceleratorRIA

Opportunities & Challenges

Richard C. YorkOctober 2004

MIT

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RIA Status

• Strong Nuclear Science community support• Nuclear Science Advisory Committee Long

Range Plan (April 2002) – RIA highest priority new facility• “The Rare Isotope Accelerator (RIA) is our

highest priority for major new construction…”

• Tied for third position for near term priorities in DOE 20-year plan (November 2003)

• RIA CD-0 – done early 2004• RIA RFP expected ??

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DOE 20-Year Facilities OutlookNear-Term Priorities

1. ITER 2. UltraScale Scientific Computing Capability 3. Tie for 3

• Joint Dark Energy Mission • Linac Coherent Light Source Protein Production & Tags• Rare Isotope Accelerator (RIA)

7. Tie for 7• Characterization & Imaging of Molecular Machines

8. CEBAF 12 GeV Upgrade 209. Energy Sciences Network (ESnet) Upgrade 2010. National Energy Research Scientific Computing Center Upgrade11. Transmission Electron Achromatic Microscope12. BTeV

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RIA Benefits

• Important benefits for basic & applied science• Study properties of a large number of isotopes

that heretofore only existed in cosmos• Quantitative information for theories of stellar

evolution & formation of elements in cosmos• Support space-based astronomical observations by

providing quantitative comparisons with theoretical predictions of stellar evolution

• Experimental data to refine theories for predicting properties of nuclei with unusual neutron-to-proton ratios

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RIA Benefits - cont’d

• Support stockpile stewardship• Only way to obtain important reaction cross

sections on unstable isotopes & to improve theoretical models

• Improved diagnostic tools via isotopic analysis of materials from underground nuclear tests

• Produce almost any isotope for radio-medical research

• Materials Science & other applications• Implantation for wear & corrosion studies• Space radiation effect studies• Material modifications – doping & annealing

techniques

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RIA Scale

• RIA project cost (in FY2001 dollars)• TEC = ~$695 M ($550 M w/o contingency)• TPC (TEC + Pre-ops, etc) = ~885 M$ over ~7-8

years• Operations - ~80 M$/year – similar to JLab

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Production of Rare Isotopes at RestTarget Fragmentation

1. Random removal of protons and neutrons from heavy target nuclei by energetic light projectiles (pre-equilibrium and equilibrium emissions).

2. Extraction of rare isotopes by diffusion; ionization and acceleration: beams of high quality.

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Classical ISOL Facility Concept• Excellent beam quality and low beam energies are possible• Limited to longer lifetimes (τ > 1s)• Isotope extraction and ionization efficiency depend on

chemical properties of element: difficult, element-specific development paths

• The most neutron-rich isotopes will have too low intensities and too short lifetimes to be suitable for re-acceleration

Postaccelerator

Isotope / isobarseparator

Thick, hot target

Transfer tube Ion source

Radioactive ion beam

Production beam

Productionaccelerator

Experiment

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Production of Rare Isotopes in Flight

hot participant zone

projectile fragment

1. Random removal of protons and neutrons from heavy projectile in peripheral collisions.

projectile

target

2. Cooling by evaporation.

projectile fragment

“radioactive beam”

Projectile Fragmentation

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Schematic of a Projectile Fragmentation Facility

• High-energy beams (E/A > 50 MeV) of modest beam quality

• Physical method of separation, no chemistry• Suitable for short-lived isotopes (τ > 10-6 s)• Low-energy beams are difficult

• Solution – stop in gas cell & reaccelerate

Fragment separator

Thin productiontarget Radioactive ion beam

Heavy ionaccelerator

Experiment

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Example Fragment Separation Technique (NSCL)

Wedge locationD = 5 cm/%R = 2500 p/∆p

100 pnA 86Kr5 kW Beam power

8 msr∆p = 5%

65% of the 78Ni is transmitted

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The Rare Isotope Accelerator (RIA) Concept

• Combines advantages of projectile & target fragmentation techniques• Use all tools developed for rare isotope research

worldwide

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General Comments

• Technical Risks• No “Show Stoppers” but significant challenges

• ~5 years - significant efforts on the driver linac -• Optimization strategies & detailed

considerations• Relatively less activity on the target and

experimental areas• Recently these arenas have seen dramatic

increase in focus• Significant challenges and issues recognized

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RIA Layout• Driver linac straight or folded (shown) – decision

based on optimization

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RIA at MSU• Over 5000 acre campus – potential sites within 5 minutes of classroom• Next generation scientists & multi-discipline synergies

North

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Driver Linac Sample Beam List• Design goal - Constant beam power

• 100 kW minimum • 400 kW if ion source capable

• Multiple charge state acceleration for >Xe

Ion A Z Final Energy(MeV/u)

H 1 1 1028 3He 3 2 777 D 2 1 622 O 18 8 560 Ar 40 18 566 Kr 86 36 510 Xe 136 54 470 U 238 92 400

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Comparison of Rare Isotope Intensities

neutron number

possible locationof neutron dripline

pro

ton

nu

mb

er

10: comparable100100 - 10,000larger than 10,000

Approximate Intensity Gains of RIA over NSCL

stable isotope

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Driver Linac Front End

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Superconducting Driver Linac

• Design driven by 400 MeV/nucleon uranium• 28+ & 29+ U injected into SC linac at 292 keV/u• Segment I

• Accelerated to ~12 MeV/u & stripped • Segment II

• 5 charge states (73±2) accelerated to ~90 MeV/u• Segment III

• Stripped and 3 charge states (88 ±1) accelerated to 400 MeV/u

I II III

Fold point

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Superconducting Structures

ßopt=0.04180.5 MHz

LegnaroMSU

ßopt=0.08580.5 MHz

ßopt=0.285322 MHz

MSU

ßopt=0.49805 MHz

MSU/JLAB

ßopt=0.63805 MHz

SNS

ßopt=0.83805 MHz

SNS

Tested – 2003Exceeded Specs.

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Superconducting Segments

6 cavity types

Cavity Type βopt f

(MHz) T

(K) Linac

Segment# Of

Cavities λ/4 0.041 80.5 4.2 I 18 λ/4 0.085 80.5 4.2 I 104 λ/2 0.285 322 2 II 208

Ellip. 0.49 805 2 III 68 Ellip. 0.63 805 2 III 64 Ellip. 0.83 805 2 III 32

Total 494

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Driver Linac Stripping Chicanes

• High symmetry – good higher-order corrections• Positioned to support longitudinal matching at

frequency changes

X XY YZ ZEntrance Exit

1st Stripping Chicane

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Transit Time Factors & Energy Gain

Stripping locations

U

H

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NSCL SRF Facility Layout

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NSCL SRF Chemistry Facility

BCP Pumping System

Temperature <15 CHeat Exchanger 5 kW Filtration 4 microns Speed 8 gpm

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NSCL SRF R&D Facility

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Segments I & II Cryostats

• Isolated vacuum• Superconducting solenoid focusing

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Low-β Cryomodule Prototype

HWR,ßopt=0.285

QWR,ßopt=0.085

0.6 T Quadrupole

9 T Solenoid

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Segment III Cryostats

Two-cavity β=0.49 prototypeTested Spring 2004

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βopt=0.49 elements

He Vessel

Tuner

PowerCoupler

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β= 0.49 Prototype Systems Test

Top Plate

Support Link

He Supply

He Return

Power Coupler

Tuner

Ti Rails

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Natural Modes/Mechanical Resonances

42 Hz 72 Hz

142 Hz121 Hz

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Cavity and microphonics circuit

Qext, fixed ≅ 1x107

Qext, transformer ≅ 105 to 4x109

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RIA Layout - BSY

Beam Switch Yard

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Driver Linac Switch Yard• Baseline – provide two beams (of same isotope) to

two targets simultaneously (µ-bunch)

-1.0

-0.5

0.0

0.5

1.0

Volta

ge

Time

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RIA Layout - Target Area

Target Area

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ISOL Target Area Concepts• 400 kW beam power – Many R&D Issues

• ~10x existing designs - major technical challenge for ISOL targets

• Infrastructure proposed suitable for ultimate 400 kW• Three (possibly staged) ISOL target stations proposed

• Redundancy & beam development & R&D to higher powers

< 400 kW primary beam

beam transport matrix

to post-accelerator

target stations withpre-separator and

focal-plane switchyard

high-resolution separators

to stopped beam area

from gas stopping station

ECR

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ISOL Target Layout

Cra

ne S

ervi

ceTr

ansf

er a

rea

Hot cell

Tele manipulator stationsRemote control room

To high resolution separators Pre-separatorTarget Plug

Plug Storage

Target service docks

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ISOL Target Station

Hg loop pipes mounted on insulators

`

Isolated HG feedthroughs

HV - electrical feedthroughs

Hg spill tank

Target ion source unit

Ion optics

vacuum pumps

to prevacuum line

vacuum duct

servicechannelsfor Hg, gas, water,electric power and instrimentation

electrical wiresmounted on insulators

`

inflatable seals

focal plane beam

switchyard

to HV platforms

pre-separator dipole magnet

1 m

Laser beams

beam lines

`

Slit system+ beam diagnostics+ optics

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Services

Target area service gallery

Access plugs

RemoteControlRoom

Target shielding

ISOL Hot Cell & Service Gallery

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Facility Classification

• Category 1 – Potential for significant off-site consequences• Category 2 – Potential for significant on-site consequences• Category 3 – Potential for localized consequences

Spallation of UC2 Target1836 MeV 3He, 100 kW, Stopping Target

7-Day Irradiation, 1-Day CoolLAHET+MCNP+ORIHET

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

0 50 100 150 200 250Fragment Mass (A)

Act

ivity

(Ci)

Calculation

DOE Cat. 2 Thresh

DOE Cat. 3 Thresh

Cat 2

Cat 3

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Fragmentation Production Area

• Targets – R&D challenge• High power density - ~ 500 kW/cm3 (400 kW

primary beam)• Small spot size – reduce geometric aberrations• ~20% of beam power lost in target• Heavy ions have high dE/dX

• Pre-separator concept• Begin to isolate downstream system from very

high radiation environment• High performance & radiation resistant magnets

required – R&D challenge

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Pre-Separator

NSCL

Target

Dipole Quad-Triplet

IsotopeSlits

Wedge

BeamDump

Beam

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PHITS 1.69 Neutron Heating Calculation

Beam

400 kW beamIron heat load = 9 kWCoil heat load = 130 W

Coil dose ~ 1 MGy/yearOrganic dose ~200 MGy/year

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RIA Layout – Low Energy Area

Low Energy Area

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Low-energy Experimental Area• Important to make design compatible with very different types of targets• Mass separators with beam cooling may be better & cheaper – R&D

Required• Post accelerator ( 10 MeV/u for A up to 240, 20 MeV/u for A<60)

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RIA Layout – High Energy Area

High Energy Area

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Fragment Separators

• High acceptance design feeding helium gas stopping station• 10 T-m, 12% momentum acceptance, 10 msr

• High resolution design feeding fast beam area• 10 T-m, 6% momentum acceptance, 8 msr• Similar to NSCL design

• Pre-separator segment• Remove primary beam & most of unwanted

fragments• R&D Challenge

• Optical design with radiation resistant magnets and beam interception elements

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Fragmentation Separation Area Layout

Gas Cell

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Gas Stopping Station

• Layout • Provides beam from gas stopping to low-energy

area• Allows use of fragment separator to send beam

to high-energy area• Good R&D progress made with NSCL gas cell

• Shown ~20-50% incident ion implanted• Shown range-compression technique workable

• Outstanding R&D questions remain• What is system efficiency?• What is rate limitation?

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Gas Stopping at the NSCL

To

buncher

Gas cell RFQ 1 RFQ 2

Degraders SkimmerNozzle Orifice

Accelerationoptics

Entrancewindow

Pressure (He): ~1 bar ~ 0.1 mbar ~10-3 mbar < 10-6 mbar

Supersonicgas jet

Beam

fromA1900

RFQ 3

• Stopping/extractions of radioactive isotopes works• Systematic studies of intensity limits• Optimized ion guiding schemes and geometries

Substantial R&D still required

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Gas Stopping Efficiency

∆P/P 0.5 %, gas_cell_1.2_50

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

1650 1670 1690 1710 1730 1750 1770 1790

18 k pps

6 k pps

2 k pps

0.4 k pps

0.04 k pps

gas-equivalent

stopping /10

Total efficiency decreases with implantation rate

Glass thickness (µm)

Known implantation rate of ions [38Ca].Measured stopping fractions: 0.2 – 0.5

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High Energy Experimental Area

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Summary

• Fully general RIA facility accommodating baseline and future capabilities has been developed

• Driver linac with beam transport• Relatively detailed design• Beam transport flexibility increase remains a

challenge• Target and experimental areas

• General designs defined & issues identified• Provides for large range of possibilities for

future capabilities• R&D priorities identified