DUSEL Theory Workshop, OSU April 4, 2008
Yuri Kamyshkov/ University of Tennessee
email: kamyshkov@utk.edu
 N N à 108 sec (in vacuum)
Sensitivity for free neutron search (observation probability)
2
 tobs 
P  Nn 

  N N 
Sensitivity for bound neutron search (in nucleon decay expts)
 tobs 
P  N n  exp  

  nucl 
 nucl  R   N2 N with R "nuclear suppression factor"
R  0.5  1023 s1 known from nuclear theory
Previous free neutron N-Nbar search experiment
Schematic layout of
HeidelbergM.- Baldo-Ceolin
ILL - Padova
- Pavia nn search experiment
M. et al., Z. Phys., C63 (1994) 409
at Grenoble 89-91
At ILL/Grenoble reactor in 89-91 by Heidelberg-ILL-Padova-Pavia Collaboration
(not to scale)
Cold n-source
25 D2
fast n, background
58
HFR @ ILL
57 MW
Bended n-guide Ni coated,
L ~ 63m, 6 x 12 cm 2
H53 n-beam
~1.7. 1011 n/s
Focusing reflector 33.6 m
Flight path 76 m
< TOF> ~ 0.109 s
No background!
No candidates
observed.
Discovery
potential :
Measured limit for2
N n  t  1.5 10 9 sec
a year of running:
Measured
limit :
 N N  0.86
 108 sec
 nn  8.6 10 sec
7
= reference unit of sensitivity
Magnetically
shielded
95 m vacuum tube
Annihilation
target 1.1m
E~1.8 GeV
~1.25 1011 n/s
Detector:
Tracking&
Calorimetry
Beam dump
Previous bound neutron N-Nbar search experiments
Experiment
Year
A
nyear (1032)
Det. eff.
Candid.
Bkgr.
 nucl , yr
Kamiokande
1986
O
3.0
33%
0
0.9/yr
0.431032
Frejus
1990
Fe
5.0
30%
0
4
0.651032
Soudan-2
2002
Fe
21.9
18%
5
4.5
0.721032
Super-K*
2007
O
245.4
10.4%
20
21.3
1.81032
*Preliminary S-K result
Observed improvement weaker
than SQRT is due to irreducible
background of atmospheric neutrinos
 nucl
Free Neutron and Intranuclear
 R   N2 N NNbar Limits Comparison
Important to know
theoretical uncertainty
intranuclear search
experiments
Free neutron
search limit
e.g. intranuclear
nn  pions with
presumably
large uncertainty
is not accounted
NNbar unique for DUSEL
Yates Ross
#5; 5137
Nuclear
reactor
as a source
of neutrons
1.5 km vacuum
flight tube
Anti-neutron
detector
Shaft #5 might not be usable
3.4 MW annular core
research TRIGA reactor
with Liquid D2 cold
neutron moderator
TRIGA =
Training
Research
Isotopes
from
General
Atomics
Neutron shaft
Detector Hall
Door
Access Tunnel
Control Room
& Electronics
Neutron Dump
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
Shaft diameter
1 km
15-20 ft
Vacuum chamber with
Active + passive magnetic shield
Annular core TRIGA reactor
LD2 cryogenic cold moderator; neutron temperature
Running time
105 Pa
1 nT
3.4 MW
35K
3-5 years
Robust detection signature nA  several pions
Annihilation properties are well modeled
Active magnetic shielding allows effect
Sensitivity increase more than
Expected background at max sensitivity
1.8 GeV
LEAR physics
ON/OFF
1000
<0.01 event
Most exciting for experiment
is a possibility of increasing
sensitivity by large factor
1,000 (or nucl 1035 years)
Conservative DUSEL
baseline configuration
based on established
technologies
Possible improvement
by on-going developments
(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 35K
is a challenge for CM theory;
non-sufficient R&D efforts
H. Shimizu, KEK/Japan
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 known
at Homestake mine  ongoing R&D
to 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
2009
2011
2015
2013
conceptual design
decision
like CD0
is needed
prelim
design
board
approve
construction
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)