Gas Cell Based Laser Ion Source for Gas Cell Based Laser Ion Source for Production and Study of Neutron Rich Production and Study of Neutron Rich

Heavy NucleiHeavy Nuclei(In (In GaGas Cell s Cell LLaser Ionization & aser Ionization & SSeparation Setup)eparation Setup)

Sergey Zemlyanoy

Flerov Laboratory of Nuclear ReactionsJoint Institute for Nuclear Research

Dubna

1st Topical Workshop on Laser Based Particle Sources 20-22 February 2013, CERN

Unexplored “north-east” area of the nuclear mapUnexplored “north-east” area of the nuclear map

fusion

fragmentation

19 known neutron-rich isotopes of cesium (Z = 55) and only 4 of platinum (Z = 78).

Above fermium (Z = 100) only proton-rich nuclei are known.

fissionfragments

Abundance of the element in the UniverseAbundance of the element in the Universe

The 11 Greatest Unanswered Questions of Physics(National Research Council, NAS, USA, 2002):

1. What is dark matter? 2. What is dark energy?

3. How the heavy elements from iron to uranium have been produced? 4. Do neutrinos have mass? …

Strong neutron fluxes are expected incore-collapse supernova explosions or in the mergers of neutron stars.

r-process and heavy neutron rich nucleir-process and heavy neutron rich nuclei

(1) difficult to synthesize(2) difficult to separate

Production on NEW heavy nuclei in the region of N=126Production on NEW heavy nuclei in the region of N=126(Zagrebaev & Greiner, PRL, 2008)

“blank spot”

82 82

Production on new heavy nuclei in the Production on new heavy nuclei in the Xe + PbXe + Pb collisions collisions

Test experiment demonstrates good agreement with our expectationsTest experiment demonstrates good agreement with our expectations

Simulation of typical experiment in the laboratory frameSimulation of typical experiment in the laboratory frame

(1) The yield of new neutron-rich isotopes is maximal at beam energy slightly above the Coulomb barrier(2) Desired reaction products are forward directed (no any grazing features)

Multi-nucleon transfer reactionsMulti-nucleon transfer reactions as a method for synthesis of heavy neutron rich nucleias a method for synthesis of heavy neutron rich nuclei

andand

Stopping in the gas with subsequent resonance Stopping in the gas with subsequent resonance laser ionizationlaser ionization

as a method for extracting required reaction products (with a given as a method for extracting required reaction products (with a given Z value) Z value)

IGISOL – Ion Guide Isotope Separation on line

Laser beams

+ ++

massseparator

cyclotronbeam

SPIG

Ni filament

He

target3-10 mg/cm2

40 kV

Time profiles of laser-ionized stable

Ni-58 from the filament

~1994

Laser-produced Ni ions recombine in a plasma created by a primary beam

>99% are neutral

We have to provide for radioactive atoms:

1. Efficient laser ionization

2. Survival of laser-produced ions in a volume around the exit hole

Weak beam, 1nA, 1ms

Strong beam, 1uA,20ms

Delay time - down to 10 ms (He)Refractory elements - !

Schematic view of setup for resonance laser ionization Schematic view of setup for resonance laser ionization of nuclear reaction products stopped in gasof nuclear reaction products stopped in gas

Gas handling- and purification system

Laser system

Mass separator front end

Pumping station

Mass separator

Accelerator beam transport

system

Gas cell

This part is at high tension of 40kV

Ion extraction

system

Detection system

Setup consist of the following subsystemsSetup consist of the following subsystems

The scheme of the front end of the GALS mass separator The scheme of the front end of the GALS mass separator subsystemsubsystem

7000 m3/h

Laser beamsLongitudinal

Laser beamsTransversal

Exit hole

Ar, He from gas purifier

Ion Collector

Ionizationchamber

Acceleratorbeam

Ion collector

SPIG

Stopping chamber

500 mbar

+

+

++

Target

Reaction products

Towards mass separator

Laserionization chamber

+

+

+

Exit hole diameter – 0.5mm/1mm

Stopping chamber – 4 cm in diameter

Laser ionization chamber – 1 cm in diameter

The aim: (by separating stopping and laser ionization chambers)

•Increasing laser ionization efficiency at high cyclotron beam current

• Increasing selectivity (collection of survival ions)

Working conditions:

-cyclotron – DC

-Ion collector – DC

-Lasers – transverse or longitudinal

The layout of the dual chamber laser ion source gas cellThe layout of the dual chamber laser ion source gas cell

The ion extraction from the gas cellThe ion extraction from the gas cell

1200 V 250V

4.7MHz

0-500V

dE ~ 0.7 eV (-210 V)

The SPIG consists of 6 rods (124 mm long and a diameter of 1.5 mm) cylindrically mounted on a sextupole structure with an inner diameter of 3 mm. The distance between the SPIG rods and the ion source is equal to 2 mm.

Cyclotron beam

Gas CellSPIG

Extraction electrode

Gas from purifier

Front end of the LISOL mass separator

Gas cell and Ion-guide systemGas cell and Ion-guide system

General requirements to the ion-guide systems look as follows: • pressure in gas cell: 100–500 mbar depending on the energy of reaction products and required extraction time;• working gas is He or Ar (the latter looks preferably because its stopping capacity and efficiency of neutralization are higher);• gas purity not lower than 99,9995%;• cell volume is about 100–200 cm3;• vacuum in intermediate camera not worse than 10-2 mbar;• vacuum in the entrance into the mass separator is 10-6 mbar; Some specific requirements, stipulated by the use of the resonance laser ionization, should also be taken into account:

• gas cell should be two-volume to separate the area of thermalization and neutralization from the area of resonance laser ionization;• extraction of ions from the cell and driving them into the mass separator have to be provided by the sextupole radio-frequency system which allows one to increase the efficiency of the setup and to perform ionization of atoms in the gas jet outside the cell; • the input-output setup must be supplied by the system of optical windows and by the system of explicit positioning (0.3 mm) of the gas cell, guide mirrors and prisms.

The pump stationThe pump station3 roots pump station at HV platform Isolating transformer for HV platform

Specifications of the pump station located in the basement:

-Pumping system: RUVAC WH 7000 roots pump with SCRELINE SP630 backing pump Leybold Vacuum.

Electrical power for the prepump : 3 X 380V, 11 kWElectrical power for the pump: 3 X 380V, 18 kWWeight : 1300 kg, Noise level : 80 dB(A) - pumps to be placed in the basement with sound isolation panels-Pumping station is placed on the high voltage platform (40kV) and electrical power for roots and backing pumps comes via the isolation transformer. - A metal fence with a door and safety switch has to be installed around the pumping station.- Vacuum gauges and the meter have to be foreseen in the basement.

The scheme of the gas handling and purification systemThe scheme of the gas handling and purification system

Gas purifierMonoTorr Phase II 3000 SAES Pure Gas, Inc.

Ar Grade 5.5 (99.9995%)

Flow meterBrooks Instrument

5860S 0.08 - 8 ln/min

Towardsgas cell

Oil-free, smallpump station

The gas purity is a key issue for efficient running of the laser ion source. The gas handling system has to be designed to supply and to control the gas flow into the gas cell. Electro-polished stainless steel tubes and metal-sealed valves have to be used in order to reduce the outgasing and the "memory effect". The system should be bakeable up to 2000C with temperature control and be pumped by a separate small oil-free pumping station. High-purity argon gas is additionally purified in a getter-based purifier to the sub-ppb level.

Gas purifying systemGas purifying system

Mass separatorMass separator

All extracted ions have charge state +1 because only neutral atoms are ionized to this state by the lasers while all “non-resonant” ions are removed by electric field before reaching the area of interaction with laser radiation. In this case the extracted particles can be easily separated by masses in dipole magnet. For low-energy (30–60 keV) beams of +1 charged ions no specific requirements are needed for the dipole magnet. It could be a standard magnet separator similar to ISOLDE II, for example: • Bending angle 40о–90о,• Bending radius of about 1–1.5 m, • Focal plane length of about 1 m,• Rigidity of about 0.5 Тm.• Dipole gap about 50-60 mm

Mass resolution is the only critical parameter which should be about 1500. Camera of the separator must have an optical input if collinear laser ionization is used with the sextupole ion-guide (SPIG).

Lens chamber

Laser ion source chamber

Movable prism

Laser Ion Source

Screen Gas handling system

HV

Detection

stable

radioactive

HV area

Fig. 11. Plan of the mass separator area

Dispersion chamber

Lens chamber

Laser ion source chamber

Movable prism

Laser Ion Source

Screen Gas handling system

HV

Detection

stable

radioactive

HV area

Fig. 11. Plan of the mass separator area

Dispersion chamber

Mass separatorMass separator

Most important specifications:

MagnetWeight : 1800 kg, Bmax :0.76 TCooling water flow: 400 l/h, pressure drop = 4 barCooling water: 15 degreesMagnet power supplyWeight : 250 kgOutput : max 300A/25VAC main input: 3 X 380V, 18.5ACooling water flow: 120 l/h, pressure drop=3barVacuum system4 turbo pumps (at front end, lens chamber, entrance of the magnet, dispersion chamber): for example Edwards STP1003C,Water cooled, 100 l/h per pumpTwo Prepumps, for example Pfeiffer MVP160-3 can be placed in the basement- Total flow for cooling water: min. 1000 l/h- Compressed air to drive small actuators and vacuum valves- Total electrical power needed : ~20 kW

Dye Ti:SaActive Medium > 10 different dyes =1 Ti:sapphire crystalcondition of aggregation liquid solid-stateTuning range 540 – 850 nm 680 – 980 nmPower < 15 W < 5 WPulse duration 8 ns 50 nsPower stability decrease during operation stable

Synchronization optical delay lines q-switch, pump power

Maintenance renew dye solutions ~ none

Comparison dye vs. possible Ti:Sa systemComparison dye vs. possible Ti:Sa system

200 300 400 500 600 700 800 900

0.10.20.51.02.05.0

10.0

wavelength nm

Ti:STi:Saa

DyeDye

2x Ti:Sa2x Ti:Sa2x Dye2x Dye

3x Ti:Sa3x Ti:Sa3x Dye3x Dye

550 600 650 700 750 800 850 900 950

0

5

10

15

20

25

30

35

effic

iency

(%)

wavelength (nm)

DyeDye

Ti:STi:Saa

The (almost) optimum RILIS Laser SystemThe (almost) optimum RILIS Laser System

Nd:YAG Dye 2

Dye 1 THG

SHG

RILIS Dye Laser System GPS/HRS

Target & Ion Source

– meter

Nd:YAG Ti:Sa 3

Ti:Sa 2

RILIS Ti:Sa Laser System

– meter

Master clock

Delay Generator

pA – meter

Faraday cup

SHG

Narrowband Dye

Ti:Sa 1 SHG/THG/FHG

Laser systemLaser system

type output power, (average) main & harmonics:(2nd ), {3rd & 4th}, W

pulse frequency, Hz

pulse length, ns

wave length, ns

Dye laser 3, (0.3) 104 10-30 213 - 850

Ti:Sapphire 2, (0.2), {0.04} 104 30-50 210 - 860

Eximer laser

30 400 10-20 308

CVL 30-50 103-104 10-30 510.6 & 578.2

Nd:YAG (80-100) 104 10-50 532

Nd:YAG laser specification (EdgeWave GmbH) Maximal average power: 90 W and 36 W respectively;Repetition rate: 10-15 kHz;Pulse duration: 8-10 ns.Divergence parameter of the green beam: M2 = 1.4;Electrical power 3.6 kW including 1.6 kW for the water chiller.

Credo dye laser specification (Sirah)Maximal average power: 20 W at fundamental wavelength, 2 W at 2nd harmonics;Line width: 1.8 GHz Pulse duration: ~7 ns Remote control of wavelength with stabilization to an external laser wavelength meter.

The layout of laser installationThe layout of laser installation

OT1-OT9 – optical tables; Nd:YAG1 and Nd:YAG2 – pump lasers; DL1-DL3 – dye

lasers; R1 and R2 – racks for electronics and water chillers; M1-M10, M22 – high power mirrors for 532nm beams; M10-M15 – high power mirrors for 355nm beams; BS1-BS4 – beam splitters for 532nm beams; M16-M21, M23-M25 – mirrors for dye laser beams; T1-T4 – telescopic zoom expanders for 532nm beams; T5 and T6 - telescopic zoom expanders for 355nm beams; L1-L6 – spherical lenses, SM1 and SM2 – spherical mirrors; BD1 and BD2 – beam dumps for IR beams; P1 and P2 – half-wave plates for 355nm; RM1-RM4 – return mirrors for reference beams; RP – reference plane; AlM1 – Al mirror; QP1 – quartz plate; RC – reference cell

DL 3

R1

DL

1

Nd:

YAG

1

DL

2

Nd:

YAG

2

R2

OT5

OT6 OT7

OT8

OT9RC

M1BS2

M2

SM1

SM2

QP1

M24RP

T1

L1

OT2

BD1 BD2

OT3

OT4

OT1

M3

M4

M5

M6

M7

M8 M9 M10 M11

BS1 BS3BS4

BS5

M12 M13

M14

M15 M16

M17

M18

M19

M20

M21M22M23

RM1

RM2

RM3

RM4

T2

T3

T4

T5 T6

L2

L3 L4

L5

L6

P1 P2

The laser system viewThe laser system view

Rooms requirements for this setupRooms requirements for this setup

Possible position of SETUP at cyclotron U400MPossible position of SETUP at cyclotron U400M

5400

3000

1160

1640

2800

Laser room

Corridor

1000

M23

pmM1

RM1

RM1a

W13500 to ion source

1260

900

Mass separator area

1100

M24

M25

OT10

OT4

Working planWorking plan

Laser

system

Front end system

Pump station

Gas purification

Separator,

detectionpreparation

mounting

commissioning

preparation

mounting

commissioning

preparation

mounting

commissioning

preparation

mounting

startup

preparation

mounting

commissioning

2012

2013

2014

2015 starting experiments

• At target thickness 0.3 mg/cm2, ion beam of 0.1 pA and setup efficiency of 10% we would be able to detect 1 event per second at cross section of 1 microbarn

• It allow as to measure decay properties at least 1 new isotope per day

• It is sufficiently not only for measurement of typical nuclear characteristics (like half-life times, decay schemes, etc.), but also for determining of nuclear charge radii (and moments) with using in-source laser spectroscopy.

ConclusionConclusion

People involved into developing and discussion of this SETUP People involved into developing and discussion of this SETUP projectproject

Leuven: M. Huyse, Yu. Kudryavtsev, P. Van Duppen

Jyväskylä : Juha Äystö, Iain Moore, Heikki Penttilä

CERN: Valentin Fedosseev

GSI: Michael Block, Thomas Kühl

GANIL: Nathalie Lecesne, Herve Savajols

Mainz: Klaus Wendt

Manchester: Jonathan Billowes, Paul Campbell

iThemba LABS: Robert Bark + 2 PhD students

Egypt: Hosam Othman

IS RAN Troitsk: Vyacheslav Mishin

FLNR JINR: V. Zagrebaev, S. Zemlyanoi, E. Kozulin, and others

People involved into developing and discussion of this SETUP People involved into developing and discussion of this SETUP projectproject