Future Penning Trap Experiments at GSI / FAIR – The HITRAP and MATS Projects

K. Blaum1,2 and F. Herfurth1 for the HITRAP and MATS Collaboration

1GSI Darmstadt, 2Johannes Gutenberg-University Mainz

Introduction

Ion traps play an important role not only in high-precision experiments on stable

particles but also on exotic nuclei. Besides accurate mass measurements they

have recently been introduced to nuclear decay studies and laser spectroscopy

as well as to tailoring the properties of radioactive ion beams. This broad usage

of trapping devices at accelerator facilities is based on the manifold advantages

of a three-dimensional ion confinement in well controlled fields: First, the

extended observation time is only limited by the half-life of the radionuclide of

interest, yielding very high precisions for instance for mass measurements.

Second, stored ions can be cooled and manipulated in various ways, even

polarization and charge breeding of the ions are possible, giving a unique tool in

order to prepare otherwise impossible experiments. Third, it is possible to create

a backing free source of radioactive nuclei and to collect light particles (e - and e+)

very efficiently, reducing a number of uncertainty in classical spectroscopic

experiments. The HITRAP and MATS Collaborations propose advanced trapping

systems at GSI and the future facility FAIR for high-precision mass

measurements, tests of QED using highly-charged heavy ions, and decay

studies on short-lived radionuclides.

General InformationFor further information contact:

produced for the planned experiments. HITRAP will use the existing GSI facility

and the ESR storage ring to decelerate heavy, highly-charged ions. At FAIR

HITRAP will be the core of the low energy ion and antiproton facility FLAIR.

MATS will be installed at the Low Energy Branch of the Super-FRS at FAIR,

where radioactive beams with up to 10 000 higher yields than anywhere else will

be available.

Experiments at HITRAP and MATS

A number of experiments are planned at HITRAP and MATS using a high-precision Penning trap. Mass

measurements will be performed at both setups using the high accuracy potential and especially at MATS the high

sensitivity. A relative mass uncertainty of 10 -9 for radioactive, short lived ions and 10-11 for stable, highly-charged ions

can be reached by employing highly-charged ions and a non-destructive Fourier-Transform Ion-Cyclotron-Resonance

(FT-ICR) detection technique on single stored ions. The use of the FT-ICR technique provides true single ion

sensitivity. This is essential to access isotopes that are produced with minimum rates and that very often are the most

interesting ones.

In order to test the predictions of quantum-electrodynamics (QED) the g-factor of the bound electron in hydrogen-like

uranium will be measured in a dedicated Penning trap. In turn, these measurements are able to deliver a new access

to fundamental constants, as for instance the mass of the electron or the fine-structure constant .

Motivation and Fields of Application

With MATS at FAIR we aim for applying

two different techniques to very short-lived

radionuclides: High-precision mass

measurements and in-trap conversion

electron and alpha spectroscopy. The

experimental setup of MATS is a unique

combination of an electron beam ion trap

for charge breeding, ion traps for beam

preparation, and a high precision Penning

trap system for mass measurements and

decay studies. Each subsystem is a

versatile tool itself and allows different

high-precision experiments resulting in a

broad physics output. For beam

preparation an ion beam cooler and

buncher will be used. A magnetic multi-

passage spectrometer is implemented for

q/A separation of the highly-charged ions.

For further details see the Technical

Proposal submitted to the FAIR.

Figure of the proposed Experimental MATS Setup

Dr. Klaus Blaum or Dr. Frank HerfurthAddress: University of Mainz, Institute of Physics,

55099 Mainz or GSI, 64291 Darmstadt

The mass and its inherent connection with

the nuclear and atomic binding energies is

a basic property of a nuclide. Thus, precise

mass values are important for a variety of

applications, ranging from nuclear-

structure studies, test of nuclear mass

formulas, to tests of the weak interaction,

QED, and of the Standard Model. The

required relative accuracy ranges from 10 -5

to below 10-10 for stable and short-lived

nuclides, which most often have half-lives

well below 1 s. Substantial progress in

Penning trap mass spectrometry has made

this method a prime choice for precision

measurements on stable and rare

isotopes. Furthermore, ion traps can be

used advantageously for precision decay

and laser spectroscopy.

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Te st- io nso urc e

Pre p a ra tio nPe nning tra p

M e a sure m e ntPe nning tra p

EBIT

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Top View G round Floor

S ide V iew

Ro o f c ra ne (2 to n)

HV C a g e

HV C a g e

HV C a g e

G round Floor

F irst F loor

HV C a g e

Te st- io nso urc e

GSI and FAIR

NuclearNuclearPhysicsPhysics

nuclear binding energies,Q-values

m/m 1·10-7

NuclearNuclearStructureStructure

shell closure, pairing, deformation, halos,

isomers

m/m 1·10-7

m/m 1·10-7

FundamentalFundamentalPropertiesProperties

tests of nuclear modelsand formulae

AtomicAtomicPhysicsPhysics

e- binding energyQED test

m/m 1·10-10

m/m < 3·10-8

WeakWeakInteractionInteractionsymmetry tests,CVC hypothesis

m/m < 1·10-7

AstroAstro--physicsphysics

nuclear synthesis,r- and rp-process

Weighingexotic

systemstrap assisted

decayspectroscopý

trap assistedlaser

spectroscopý

GSI stands for state

of the art research on

heavy, highly-

charged ions and

radioactive nuclei.

FAIR (Facility for

Antiproton and Ion

Research) is the

future of GSI. The

future facility is going

to provide ion beams

with currently unique

intensity and energy

so that intensive

secondary beams -

e.g. bare uranium,

exotic nuclei or

antiprotons - can be

FAIR

NESR

SIS 18

FRS

ESR

ESR

UNILAC

SIS 100/300

HESR

SuperFRS

CRRESR

LEB

The HITRAP project

HITRAP will be installed at GSI in order to provide and study bare heavy nuclei or heavy nuclei

with only few electrons at very low energies or even at rest. Highly-charged ions will be

produced by stripping at relativistic energies. Another possibility is the production of radioactive

nuclei using the fragment separator FRS. After electron cooling and deceleration in the

Experimental Storage Ring ESR the ions are ejected out of the storage ring at 4 MeV/u and

further decelerated in a combination of an IH and RFQ structure. Finally, they are injected into

a Penning trap where the ions are cooled to 4 K. From here, the ions can be transferred in a

quasi dc or in a pulsed mode to different experimental setups. These are for instance traps to

measure the g-factor of the bound electron or the mass of the ion. Other setups are designed

to investigate the electronic structure of heavy, highly-charged ions in detail in slow collisions

with helium atoms or with surfaces of insulators and semi-conductors.

UNILAC

SIS

ESR

FRS

stripper

Linear Decelerator

CoolerPenning Trap

4 MeV/u6 keV/u

400

Me

V/u

Exp

erim

ents

1 G

eV

/u

2 keV/u

MATS and HITRAP are international collaborations. More than 16 institutes are part of them and cooperate in the design and construction . A letter of intent for the MATS project was submitted in April 2004 to the FAIR committee and approved . A cost review board evaluated recently very positive the financial part of MATS. Already since spring 2004 HITRAP has been an approved midterm project of GSI and construction of the decelerator and the cooler trap have been started in 2005. First experiments at HITRAP are scheduled for 2007.