Transcript Possibility for the production and study of heavy neutron

Design of a new setup for extraction of reaction
products by means of their stopping in gas and
subsequent resonance laser ionization
Sergey Zemlyanoy
Flerov Laboratory of Nuclear Reactions
Joint Institute for Nuclear Research
35th meeting of the JINR PAC for Nuclear Physics
Jan.26-27, 2012, Dubna.
Production of new heavy nuclei in Xe + Pb collisions
Programme Advisory Committee for Nuclear Physics
34th meeting, 16–17 June 2011
•
•
•
•
•
Valery Zagrebaev presents the talk:
Possibility for the production and study of heavy neutron-rich nuclei
formed in multi-nucleon transfer reactions
The PAC discussed the proposal of the Flerov Laboratory, presented by
V. Zagrebaev, on the synthesis of heavy neutron rich nuclei formed in lowenergy multi-nucleon transfer reactions. The use of this method opens a
new field of research in low-energy heavy-ion physics, namely, the
production and study of new neutron rich heavy nuclei playing a key role in
the r-process of nucleosynthesis. The development of an experimental setup based on the method of stopping reaction fragments in gas and on their
subsequent selective resonance laser ionization is proposed. With such a
method atoms of required elements can be selected. The method is already
used in several laboratories for separation and study of light exotic nuclei
and fission fragments. Because of the capability of selecting ions of specific
atomic numbers, this set-up can also be employed in other studies, like the
unknown charge distribution of the products of quasi-fission. The PAC
emphasizes that the proposed experimental method is feasible.
Recommendation.
The PAC strongly recommends starting to work on the details of this
proposal within the Flerov Laboratory right away.
During period from last PAC session it was performed
•
•
•
•
•
•
Detailed Laser scheme of setup.
Scheme of gas part of setup, consisting of: front end system, gas cell, SPIG
system, evacuation system, gas cleaning system etc.
Drawings for all elements of gas part of setup
The different possibilities of Setup position at FLNR U-400M cyclotron
have been considered and 2 variants developed more detailed
The International Workshop on “Resonance Laser Separation of Nuclear
Reaction Products” was held on 6-7 December at Flerov Laboratory.
Leading scientists in this field of research from Leuven, Jyvaskyla, GANIL,
CERN, GSI, Mainz and iThemba took part in the Workshop.
During the Workshop the project on production and study of heavy neutron
rich nuclei formed in multi-nucleon transfer reactions was discussed along
with details of the corresponding setup. The project have been examined by
the experts and got their approval.
Schematic view of setup for resonance laser ionization
of nuclear reaction products stopped in gas
Setup consist of the following subsystems
Accelerator
beam transport
system
Detection
system
Mass separator
Ion
extraction
system
Gas cell
Mass separator
front end
Pumping
station
This part is at high
tension of 40kV
Gas handling- and
purification system
Laser system
The scheme of the front end of the LISA mass separator
subsystem
7000 m3/h
The layout of the dual chamber laser ion source gas cell
Ar, He
from gas
purifier
Laser beams
Longitudinal
Accelerator
beam
Stopping
chamber
Target
+
+
+
500 mbar
Reaction products
Ionization
chamber
Ion
collector
+
Laser
ionization
chamber
Laser beams
Transversal
+
+
Exit hole
Ion Collector
SPIG
+
Towards mass
separator
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 ion extraction from the gas cell
dE ~ 0.7 eV
4.7MHz
0-500V
1200 V
(-210 V)
250V
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.
Front end of the LISOL mass separator
Cyclotron beam
Extraction
electrode
Gas Cell
SPIG
Gas from purifier
Gas 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.
Production cost of the gas cell and ion output systems is about 800 k$.
Specifications of the pump station located in the basement:
-Pumping system: RUVAC WH 7000 roots pump with SCRELINE SP630 backing pump
-(from Oerlikon Leybold Vacuum Gmbn) is taken as example.
Electrical power for the prepump : 3 X 380V, 11 kW
Electrical power for the pump: 3 X 380V, 18 kW
Weight : 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 pump station
3 roots pump station at HV platform
Isolating transformer for HV platform
The scheme of the gas handling and purification system
Ar Grade 5.5
(99.9995%)
Gas purifier
MonoTorr Phase II 3000 SAES
Pure Gas, Inc.
Flow meter
Brooks Instrument
5860S 0.08 - 8 ln/min
Towards
gas cell
Oil-free, small
pump 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 system
Mass 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 Т.m.
• Dipole gap about 50-60 mm
HV area
Laser ion source
chamber
Lens chamber
stable
Laser Ion Source
Detection
radioactive
Movable prism
Dispersion chamber
HV
Screen
Gas handling system
Fig. 11. Plan of the mass separator area
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).
Production cost of such mass separator is about 250 k$.
Mass separator
Most important specifications:
Magnet
Weight : 1800 kg,
Bmax :0.76 T
Cooling water flow: 400 l/h, pressure drop = 4 bar
Cooling water: 15 degrees
Magnet power supply
Weight : 250 kg
Output : max 300A/25V
AC main input: 3 X 380V, 18.5A
Cooling water flow: 120 l/h, pressure drop=3bar
Vacuum system
4 turbo pumps (at front end, lens chamber, entrance of the magnet, dispersion chamber):
for example Edwards STP1003C,Water cooled, 100 l/h per pump
Two 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
Comparison dye vs. possible Ti:Sa system
Active Medium
condition of aggregation
Tuning range
Power
Pulse duration
Power stability
Dye
> 10 different dyes
liquid
540 – 850 nm
< 15 W
8 ns
decrease during operation
Synchronization
Maintenance
optical delay lines
renew dye solutions
35
Dye
Ti:S
a
2x Dye
2x Ti:Sa
3x Ti:Sa
3x Dye
4x Ti:Sa
200 300 400 500 600 700 800 900
wavelength nm
30
efficiency (%)
10.0
5.0
2.0
1.0
0.5
0.2
0.1
Ti:Sa
=1 Ti:sapphire crystal
solid-state
680 – 980 nm
<5W
50 ns
stable
q-switch, pump
power
~ none
25
20
Ti:S
a
15
10
5
0
Dye
550 600 650 700 750 800 850 900 950
wavelength (nm)
The (almost) optimum RILIS Laser System
l – meter
Nd:YAG
Master
clock
Dye 2
SHG
Dye 1
SHG
THG
Narrowband Dye
RILIS Dye Laser System
Delay
Generator
GPS/HRS
RILIS Ti:Sa Laser System
Nd:YAG
Target &
Ion Source
Ti:Sa 3
Faraday cup
Ti:Sa 2
Ti:Sa 1
SHG/THG/FHG
l – meter
pA – meter
Laser system
type
output power,
(average) main &
harmonics:
(2nd ), {3rd & 4th}, Wt
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: 12 GHz
Pulse duration: ~7 ns
 Remote control of wavelength with stabilization to an external laser
wavelength meter.
Production cost of the laser system with three-step resonance ionization
(combined with the corresponding optical scheme) is about 950 k$.
The layout of laser installation
OT2
T1
BS3
DL 1
OT7
T2
L3
L4
BS2
M14
P2
M6
BS4
T5
Nd:YAG 1
M17
M5
M13
BD2
M11
P1
M3
M10
BD1
OT6
L2
L1
RM1
RM2
RM3
RM4
M20
M18
M8
M21
L5
L6
T6
T3
DL 3
BS1
M16
M22
M23
M24
M25
M19
SM1
DL 2
OT1
M2
OT4
SM2
Nd:YAG 2
M1
OT5
OT3
OT8
T4
AlM1
OT9
QP1
RP
R1
M12
M4
R2
M15
M7
M9
RC
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
The laser system view
Rooms requirements for this setup
Possible position of SETUP at cyclotron U400M
6000
Laser room
RM1a
M26
Mass
separator area
1160
660
4000 to ion source
M27
2560
Corridor
OT10
1260
RM1
M22
1000
W1
3500
1100
OT4
1400
pmM1
Possible position of SETUP at cyclotron U400M
5400
RM1a
pmM1
3000
1160
1000
OT10
Corridor
1260
M23
3500 to ion source
M25
RM1
2800
1640
W1
OT4
Mass
separator area
900
M24
1100
Laser room
Price of the equipment for the SETUP Laser System
Position
Supplier
Model
Price/unit
Euro
Quantity
Total cost
Euro
Nd:YAG laser
Edge Wave GmbH, Germany
IS-XXX
140000
2
280000
Dye laser
Sirah Laser- und
Plasmatechnik,Germany
Credo
60000
3
180000
Stabilized HeNe single mode
laser
Edmund Optics
NT59-939
5000
1
5000
Lasers
Sub-total "Lasers"
Instruments and electronics
Sub-total "Instruments and
electronics"
Optomechanics
Sub-total "Optomechanics"
Optics
Sub-total "Optics"
465000
Wavemeter, powermeters,
photodiods, CCD cameras,
control electronics, etc.
38500
Optical tables, microtables,
mounts, microdrives, etc.
67500
Telescopes, lenses, mirrors,
prizmas,doubl-tripl. crystals,etc.
39300
Safety
Sub-total "Safety"
18700
Reference chamber
30000
TOTAL:
659000
Price of the subsystems equipment for the SETUP
Position
Mass separator front end
Price
Euro
Position
Price
Euro
Isolation quarts tube, remote control needle valve,
electronics, gas line towards gas cell)
15000
15000
Backing power supplies and temperature control
5000
Electronics and mechanics for the gas cell
15000
Sub-total "Gas handling and purification system"
77000
Pumping station (roots pump, prepump, bak.pump,)
200000
High voltage platform with isolation transformers
30000
Sub-total
290000
Laser ion source and extraction chambers
20000
Laser ion source
10000
Stabilized power supply
SextuPole ion guide (SPIG) structure
5000
Electronics and mechanics SPIG (RF, DC pow. suppl.)
12000
Pumps for the extr.chamb.
30000
Sub-total
47000
Lens chamber
20000
Diagnostics (mov. Faraday cup and prism, electronics)
Accelerator beam transport system
Movable Faraday Cup, movable or rotable energy
degraders, electronics
12000
Remote control vacuum valves, turbo molecular pump
with baking pump
25000
Sub-total "Accelerator beam transport system"
37000
Dispersion chamber and Detection system
Dispersion chamber
20000
10000
Turbo molecular and baking pumps pressure gauges and
meters
25000
Power supply, high voltage insulator
12000
Tape station for radioactive isotopes
20000
Pumps for the lens chamber
30000
Gamma, beta or alpha detectors
40000
Current meter (noise level< 1pA)
8000
Oil-free pumping station
17000
Beam diagnostics (Faraday cup, needle scanner,
adjustable diaphragm in the focal plane)
15000
Sub-total
80000
Detectors and housing for stable beam
8000
Gas handling and purification system
Gas purifier, gas flow meter, valves, electro polished
tubes, pressure gauges and meters
40000
Sub-total"Dispersion chamber and Detection system"
128000
Dipole magnet
80000
Total
739000
Financial plan, k$
Laser
system
2012
2013
600
390
Front end
system
265
Pump
station
145
2014
240
Gas
purification
100
Separator,
detection
250
Total
600
800
590
Total: 1990 k$
Working plan
Laser
system
prepa
ration
mou
nting
Front
Pump
end system station
start
up
prepa
ration
mou
nting
start
up
prepa
ration
mou
nting
start
up
Gas
purification
Separator,
detection
prepa
ration
prepa
ration
2012
2013
2014
2015
starting experiments
mou
nting
start
up
mou
nting
start
up
Report of the Experts
•
on the FLNR project on production and study of heavy neutron rich nuclei
formed in multi-nucleon transfer reactions by means of their stopping in gas
cell and subsequent resonance laser ionization
•
The International Workshop on “Resonance Laser Separation of Nuclear •
Reaction Products” was held on 6-7 December at Flerov Laboratory of
Nuclear Reactions JINR. Leading scientists in this field of research from •
Leuven, Jyvaskyla, GANIL, CERN, GSI, Mainz, iThemba and Troitsk took
part in the Workshop and made contributions on the current status of these
investigations in their centers. During the Workshop the FLNR project on
production and study of heavy neutron rich nuclei formed in multi-nucleon
transfer reactions was discussed along with details of the corresponding
setup for extraction of reaction products by means of their stopping in gas
cell and subsequent resonance laser ionization. The project was undergone
an examination by the experts and got their approval. The discussion on the
details of the project has been initiated by the decision of the JINR PAC on
Nuclear Physics in June 2011.
•
Experts made a number of recommendations on detailed parts of the project
and optimal choosing of setup components: type and initial configuration of
laser system, construction of front-end system and gas cell, importance of
adequate gas purifying system etc.
•
It was stressed by experts the following:
•
The proposed physics program is rather ambitious. These studies allow
investigating unexplored area of heavy neutron rich nuclei, helping to
understand the r-process of astrophysical nucleogenesis near the last
“waiting point”. The method proposed for production of heavy neutron rich
nuclei, namely, the low-energy multi-nucleon transfer reactions, looks
promising and adequate; the calculated cross sections of these reactions look
quite realistic.
•
The setup proposed, its configuration and components are quite feasible and
correspondent the problem. Analogous setups already successfully operated
in some facilities for another investigations and reactions type.
–
The chosen laser system (YAG + DYE) with following extension to
(YAG +TiSa) allow performing an efficient ionization of new
neutron rich isotopes, giving the possibility of their selection by
atomic number and even by isomers.
–
Gas cell with indicated main parameters (pressure 100-500 mbar of
Ar (He), double chambers) will provide efficient stopping and
guiding of reaction products to mass separator.
–
Basic mass separator parameters (with the resolution not less than
1500) fulfill the goal of isotope separation by mass.
•
The total efficiency of setup could be of order from few to tens percent.
•
The setup definitely could be build up during the period not exceeding 3
years (depending on financial schedule).
•
Required funding of amount ~2M$ looks absolutely feasible and reasonable.
The all experts strongly recommend constructing this setup at FLNR
JINR. Many of experts show an interest to participate in realization of
this project and forthcoming experiments.
Proponents: V. Zagrebaev, S. Zemlyanoi and E. Kozulin
Experts:
Michael Block (GSI, Darmstadt, Germany)
Valentine Fedosseev (CERN, Switzerland)
Iouri Koudriavtsev (KUL, Leuven, Belgium)
Nathalie Lecesne (GANIL, Caen, France)
Vyacheslav Mishin (ISAN, Troitsk, Russia)
Iain Moore (JYFL, Jyväskylä, Finland)
Herve Savajols (GANIL, Caen, France)
Klaus Wendt (Institut für Physik Johannes
Gutenberg-Universität, Mainz, Germany)
On 24 January 2012 the design of
setup for extraction of reaction
products by means of their
stopping in gas and subsequent
resonance laser ionization have
been considered by Technical
Council of Flerov Laboratory of
Nuclear Reactions, JINR and
approved.
Conclusion
• At target thickness 0.3 mg/cm2, ion beam of 0.1 pmA 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.
People involved into developing and discussion of this SETUP
project
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
IS RAN Troitsk: Vyacheslav Mishin
FLNR:
V. Zagrebaev, S. Zemlyanoi, E. Kozulin, and others
People involved into developing and discussion of this SETUP
project
Supplementary
r-process and heavy neutron rich nuclei
(1) difficult to synthesize
(2) difficult to separate
Production of NEW heavy nuclei in the region of N=126
(Zagrebaev & Greiner, PRL, 2008)
“blank spot”
IGISOL – Ion Guide Isotope Separation on line
Time profiles of laser-ionized stable
Ni-58 from the filament
Ni filament
He
+
Laser
beams
target
3-10 mg/cm2
+
SPIG
40 kV
+
cyclotron
beam
~1994
mass
separator
Weak beam,
1nA, 1ms
Delay time - down to 10 ms (He)
Refractory elements - !
Strong beam,
1uA,20ms
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
Setup position at U-400M cyclotron
Required beams of accelerated ions
(the ion beams available at FLNR are well satisfied our requirements)
Ions: 16,18О, 20,22Ne, …48Ca, 54Cr, …86Kr, 136Xe, 238U
(i.e., quite different depending on the problem to be solved).
Beam energies: 4,5 – 9 MeV/nucleon (slightly above the Coulomb barrier)
Beam intensity: not restricted (up to 1013 pps).
Beam spot at the target: 3–10 mm in diameter (not very important).
Beam emittance: 20p mm mrad.
Targets: different, including actinides Th, U, Pu, Am, Cm.
The setup consists of the following elements (units)
- front end system including:
gas cell,
system for extraction of the cooled ion beam,
electrostatic system for final formation and acceleration of the ion beam
(800 k$)
- laser system
(950 k$)
- mass-separator
(250 k$)
- system for delivery and cleaning of the buffer gas inside the gas cell,
- vacuum system,
- high voltage and radio frequency units,
- diagnostic and control systems for the ion beam.
Schematic view of setup for resonance laser ionization
of nuclear reaction products stopped in gas
Laser System
Max. Rep. Rate – 200 Hz
Excimer lasers
Dye lasers
SHGs
Reference cell
Yu.Kudryavtsev,
SMI06, March 2728, 2006
Towards LIS, 15 m
4/20
Energy (eV)
LISOL Laser Ion Source
Towards mass
separator
4
SPIG
–210V
Target (~ mg/cm2)
Exit hole
0
Cyclotron
beam
Ar 500mbar
Ar/He
from gas
purifier
Ion source selectivity - Laser ON/OFF:
30-80 for proton-induced fission reactions
100-200 for fusion evaporation reactions
Filament
Gas cell for fusion
reactions
Laser
beams
Thermalisation in a buffer gas cell (500 mbar Ar/He)
• Neutralisation (>99%)
• Resonant laser ionization: Z-selection (isomer)
• Extraction using gas flow, transport using RF ion guide
• Mass separation: A/Q selection
Plasma created in the cell does
not allow to collect not
neutralized ions and causes
recombination of laser-produced
ions
Pulsed operation mode
Cyclotron
on
off
off
on
Laser
Separator
on