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Yuri Kamyshkov/ University of Yuri Kamyshkov/ University of TennesseeTennessee
email: [email protected] email: [email protected]
DUSEL Theory Workshop, OSU April DUSEL Theory Workshop, OSU April 4, 20084, 2008
810 sec (in vacuum)N N à
Sensitivity for free neutron search (observation probability)
2obs
nN N
tP N
Sensitivity for bound neutron search (in nucleon decay expts)
exp
obsn
nucl
tP N
2 with "nuclear suppression factor"nucl N NR R
known from nuclear theory23 10.5 10 s R
At ILL/Grenoble reactor in 89-91 by Heidelberg-ILL-Padova-Pavia Collaboration M. Baldo-Ceolin M. et al., Z. Phys., C63 (1994) 409
Previous free neutron N-Nbar search experiment Previous free neutron N-Nbar search experiment
No background! No candidates observed.Measured limit for a year of running:
80.86 10 secN N
= reference unit of sensitivity
Previous bound neutron N-Nbar search experiments Previous bound neutron N-Nbar search experiments Previous bound neutron N-Nbar search experiments Previous bound neutron N-Nbar search experiments
Experiment Year A nyear (1032) Det. eff. Candid. Bkgr. nucl , yr
Kamiokande 1986 O 3.0 33% 0 0.9/yr 0.431032
Frejus 1990 Fe 5.0 30% 0 4 0.651032
Soudan-2 2002 Fe 21.9 18% 5 4.5 0.721032
Super-K* 2007 O 245.4 10.4% 20 21.3 1.81032
Observed improvement weaker than SQRT is due to irreducible background of atmospheric neutrinos
*Preliminary S-K result
2nucl N NR
Important to know theoretical uncertainty
Important to know theoretical uncertainty e.g. intranuclear
nn pions with presumably large uncertainty is not accounted
e.g. intranuclear nn pions with presumably large uncertainty is not accounted
intranuclear searchexperiments Free neutron
search limit
#5; 5137#5; 5137YatesYates RossRoss
Nuclear reactoras a source of neutrons
1.5 km vacuum flight tube
Anti-neutrondetector
NNbar unique for DUSELNNbar unique for DUSEL
Shaft #5 might not be usable
3.4 MW annular coreresearch TRIGA reactor with Liquid D2 cold neutron moderator
TRIGA =TrainingResearchIsotopesfrom General Atomics
Control Room & Electronics
Detector Hall
Neutron Dump
Neutron shaft
Access Tunnel
Door
and not Horizontal and existing high-power reactors?
First, one needs RESEARCH not POWER reactor since by design virtue neutron fluxes are higher in former
Second, most important reason: vertical gravity produces devastating effect on the cold horizontal neutron beam vertical layout doesn’t suffer from this effect, thus 3.5 MW TRIGA is more efficient that largest 100 MW research reactor HFIR at ORNL
There are no research reactors with the cold beam available; they are all occupied by “fundamental” material research
Vertical flight path 1 km
Shaft diameter 15-20 ft
Vacuum chamber with 105 Pa
Active + passive magnetic shield 1 nT
Annular core TRIGA reactor 3.4 MWLD2 cryogenic cold moderator; neutron temperature 35K
Running time 3-5 years
Robust detection signature nA several pions 1.8 GeV
Annihilation properties are well modeled LEAR physics
Active magnetic shielding allows effect ON/OFF
Sensitivity increase more than 1000
Expected background at max sensitivity <0.01 event
Conservative DUSELbaseline configurationbased on establishedtechnologies
Possible improvement by on-going developments
Most exciting for experiment is a possibility of increasing sensitivity by large factor 1,000 (or nucl 1035 years)
Most exciting for experiment is a possibility of increasing sensitivity by large factor 1,000 (or nucl 1035 years)
(a) Larger shaft length
(b) Larger reactor power
(c) New reflector quality (developments at KEK/Japan)
(d) New “colder” moderator thermalizing neutrons to lower temperatures
Thermalization of n to the temperatures lower that 35Kis a challenge for CM theory;
non-sufficient R&D efforts
H.
Shi
miz
u, K
EK
/Jap
an
Economically possible in future
Can NNbar create a background for other DUSEL experiments?
Neutrinos ? For reactor located at the distance 2 km from the DUSEL main campus reactor antineutrino flux is not larger (e.g. by scaling from KamLAND) than solar neutrino flux
Might be still essential for CC antineutrino detection experiments at DUSEL (e.g. geo-neutrinos)
Thermal neutrons? can be easily shielded down to the environmental level. The environmental thermal neutron level is not precisely knownat Homestake mine ongoing R&Dto measure it and then we will have to make sure that TRIGA reactor will not increase this level.
Attenuation of thermal neutron flux by concrete shield
North Carolina State University: A.I. Hawari, B.W. Wehring, A. Young
Indiana University: W.M. Snow, C. M. Lavelle
University of Tennessee: W. Bugg, H.L. Dodds, Y. Efremenko, G. Greene, Y. Kamyshkov, S. Pfiffner
California State University at Dominguez Hills: K. Ganezer, J. Hill
Oak Ridge National Laboratory: G. Flanagan, J.O. Johnson, K. Williams
Los Alamos National Laboratory: T. Haines, A. Saunders
National Institute of Standards and Technology: Pieter Mumm
CNA Consulting Engineers: L. Petersen
International Collaborators: KEK, PNPI, Dubna, ILL, Swiss Neutronics
The group has experience and expertise in large projects construction (L3 /LEP Hadron Calorimeter, KamLAND) participation in large underground experiments (UT, CSUDH) large scale underground construction (CNA Engineering: MINOS,S1) reactor licensing, commissioning, operations (NCSU and ORNL) cold neutron sources and cold neutron experiments (IU, NCSU, UT) neutron technologies like supermirrors and mag. shield (IU, UT) neutron transport simulations (NCSU, ORNL, UT) intranuclear NNbar transition search (CSUDH) particle detector design, construction, simulations, cost estimate, etc.
construction feasibility
conceptual design
prelimdesign
boardapprove
construction
2009 2011 2013 2015
decision like CD0is needed
Vertical experiments at DUSEL are non-traditional “other uses”. Unique feature of DUSEL among other underground labs.
Homestake PAC received in 2005 following “vertical” LOIs:
#7 Search for neutron to antineutron transitions (Yu. Kamyshkov/UT)
#23 Study of diurnal Earth rotation (W. Roggenthen / SDSMT)
#33 Physics of cloud formation (J. Helsdon / SDSMT)
New Vertical LOIs (2007):
# Cold atom interferometry for detection of gravitational waves (M. Kasevich / Stanford U)
# Search for transitions to mirror matter (n n) Mirror matter is an alternative explanation of the dark matter (A. Serebrov / PNPI)