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Commissioning of the n_TOF second
experimental area at CERN
Lucia Anna Damone, INFN Bari, on behalf of the n_TOF Collaboration
101o Congresso Nazionale della Societa’ Italiana di Fisica, Roma, 21-25 Settembre 2015
Outline
• The n_TOF project
• The facility
• Flux measurement
• Beam profile measurement
• Conclusions
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
The n_TOF Collaboration
CERN
~ 30 Institutions
>100 Researchers
+ Newcomers
Technische Universitat Wien
Austria
IRMM EC-Joint Research Center, Geel
Belgium
IN2P3-Orsay, CEA-Saclay
France
KIT – Karlsruhe, Goethe University, Frankfurt
Germany
Univ. of Athens, Ioannina, Demokritos
Greece
INFN Bari, Bologna, LNL, LNS, Trieste, ENEA – Bologna
Italy
Tokyo Institute of Technology, JAEA
Japan
ITN Lisbon
Portugal
Charles Univ. (Prague)
Czech Republic
High accuracy measurements Univ. of Lodz
of neutron induced reaction IFIN – Bucarest
cross-sections
*
(n,f), (n,cp), (n,g)
Poland
Rumania
INR – Dubna , IPPE – Obninsk *
Russian Fed.
CIEMAT, Univ. of Valencia, Santiago de Compostela,
University of Cataluna, Sevilla
Spain
University of Basel, PSI
Switzerland
Univ. of Manchester, Univ. of York
UK
L. Damone, Commissioning of the n_TOF second experimental area at CERN, SIF 2015, Roma 21-25 Settembre 2015
n_TOF measurements at glance
Nuclear energy
(fission products &
Structural material)
Nuclear Astrophysics
(stellar nucleosynthesis and BBN)
Astrophysics
Advanced nuclear reactors
(actinides)
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
The n_TOF facility (1/2)
EAR1
n_TOF is a spallation neutron
source based on 20 GeV/c
protons from the CERN PS
hitting a Pb block (~360
neutrons per proton).
185 m
flight path
Experimental area at 185 m
Booster
1.4 GeV
PS 20 GeV
Linac
50 MeV
Main feature:

extremely high instantaneous neutron flux (105 n/cm2/pulse).

very convenient for measurements of radioactive isotopes,

low cross sections,

Isotope available in small quantity
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
The n_TOF facility (2/2)
Experimental Area 2 (EAR2) is a new measuring station placed
(vertically) at 20 m from spallation target.
• Higher fluence, by a factor of 30, relative to EAR1.
EAR2
• The shorter flight path implies a factor of 10 smaller time-of-flight.
• Global gain by a factor of 300 in the signal/background ratio for
radioactive isotopes!
The huge gain in signal-to-background ratio in EAR2 allows to measure
radioactive isotopes with half lives as low as a few days.
20 m
EAR1
20 GeV/c
protons
Spallation
Target
185 m
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Commissioning of EAR2
The new beam line has been characterized in terms of flux and beam profile by means of
several detection systems, namely silicon based devices and gaseous detectors.
The detectors are equipped with different neutron converters placed in front of the sensible
layer or volume
Reaction
Energy range of standard
By combining the results of different detection system is possible to reach accuracy as low as
few percent (or less). FUNDAMENTAL TO NORMALIZE DATA
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Setup for flux measurement @n_TOF-EAR2
Silicon Monitor (SiMon2)
MGAS detectors (LiF, 235U,10B)
• LiF converter 105 mg/cm2
few mm gas gap
• 4 single pad silicon detectors 3x3 cm2
Si
Si
t
6LiF
neutrons
a
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Analisys details
GEANT4 simulation to determine efficiency
Selection cuts to reject background events
t
a
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Results for flux measurements
Agreement between detectors is being investigated and an official evaluation of the n_TOF flux in
experimental area 2 is going to be released.
At this stage of the analysis the agreement between detectors varies from 1% to 8%
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Comparison neutron flux EAR2/EAR1
x30
Possibility to study isotopes with very short half life (days)
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Beam profile detector
The spatial distribution on neutrons as a function of energy has been measured by means of
a double side silicon strip detector (DSSSD).
•
•
•
•
16 x 16 Si sensor strips
3 mm wide strips, 500 mm thick
50 x 50 mm² X-Y grid
LiF converter
• Selection of tritons
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Beam profile measured
The neutron beam has a Gaussian profile in transversal plane.
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Beam profile measured
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015
Conclusions
•
There is need of accurate new data on neutron cross-section both for nuclear
astrophysics and advanced nuclear technology (and nuclear medicine, fundamental
physics..)
•
Since 2001, n_TOF@CERN has provided an important contribution to the field, with
an intense activity on capture, fission and n-charged particle measurements.
•
A second new (and more intense flux) experimental area is now available.
•
The commissioning of EAR2 has been performed in 2014, particularly in terms of
energy and spatial distribution of neutrons.
•
The measurements confirm the enhancement of flux in EAR2 with respect EAR1.
•
EAR2 opens new perspectives for frontier measurements on short-lived
radionuclides.
L. Damone, Commissioning of the n_TOF second experimental area at CERN , SIF 2015, Roma 21-25 Settembre 2015