ESTB TEST BEAM PROPOSAL T-509

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Nov 15, 2013 (3 years and 8 months ago)

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1

ESTB
TEST
BEAM PROPOSAL

T
-
509


Date:

4.
2
5
.2013

Title:

Measurement of neutron flux from the beam dump




Principal Investigator
:


J. Va’vra

Institution
:

SLAC

Email:


jjv@slac.stanford.edu


Telephone:


x 2658

Members
:

B.
Ratcliff, W. Wisniewski
, S. Luitz, M. E. Monzani


Description of Physics Goals:


Initially
, before anything is built,

w
e want to measure
the

neutron flux coming from the
beam dump using two neutron detectors, one sensitive to a neutron capture for energies
between 10keV and 500keV

(EJ
-
254)
, and one
sensitive to
,

neutron energies
between

8
00keV

and
10

MeV

(EJ
-
210)
.

These counters will be placed

to
count
neutrons coming
in

backward direction

from the target,

see Fig.1.
We want to compare these measured
rates with
the
Fluka simulation

[1]
.
The purpose of this first testing period is to determine
if the neutron
flux is

calculated correctly ussing

Fluka, and if the
beam
flux would be

useful for
several
planned

Dark matter TPC tests.

We plan to cross
-
check the Fluka
calculations by Geant 4 simulation.


In subsequent tests we will be testing
the

sensitivity of liquid Argon (LAr) or liquid
Xenon (LXe)

TPC
detectors using
slow

neutrons. The LAr TPC detectors will be brought
in from LLNL

(see Fig.2)
, and the LXe TPC will be provided by the LZ collaboration.
We will measure nuclear recoils of neutrons from
either Ar or Xe nuclei
.
The recoiling
neutron ang
les

will be measured in an array of liquid scintillator counters

to determine
the kinematics of the problem
.
These tests are ye
t to be designed in detail, although the
LLNL test setup
ha
s already
been
used in a neutron test beam [
2
].

[1]
L.
Y. Nicolas, Firs
t Look at Neutron Production at the ESA Beam Dump,
4.14.
2013
.

[2]
S. Sangiorgio, LLNL Advanced Detector Group, Talk at SLAC, Feb. 20, 2013
.






2


Detailed
Description of
Experimental
Apparatus:


-

This initial test position is shown on Fig.1.

W
e will use NIM electronics and
LabView to read out a digital oscilloscope.
For this test we do not need to install
any shielding as we take neutrons coming backward from the target. The initial
test will use
NIM electronics and a scaler, gated by a delayed

strobe, to evaluate
the

neutron rate as a function of the

neutron TOF. It will also use
a digital scope

read out b
y
LabView for more sophisticated waveform analysis.

Figure
s

3

a&b
show

the neutron detection efficiency for slow neutrons

and fast neutrons
.

One can
see that one deals with very small numbers at a level of ~1% or less.

-

For final tests, w
e
will

need riggers to install the shielding blocks
, and

we need to
secure them for earth q
uaking. We also need to errect a polyethylene neutron beam
dump near the ESA wall


see Fig.1. Figure
2

shows the LAr test setup prepared
by LLNL.

We

will
provide
additional information about these tests

later
.


Preferred
Beam
Parameters
:


Beam Paramete
rs

Value

Comments

Particle Type

electrons


Energy (2
-
13 GeV)

13 GeV


Rep Rate (1
-
5 Hz nominal,

b
ursts up to 120 Hz)

Nominal, can take

rate

bursts

up to 120 Hz


Charge per pulse or number of electrons/pulse

10
4

-

10
9

electrons
/pulse


Energy Spread

nominal


Bunch Length r.m.s.

nominal


Beam Spot size, x
-
y, emittance

nominal



The way secondary particles are produced at ESTB has the inherent risk that the full
power beam might be delivered to your experiment. This can happen when the energies
between LCLS and the A
-
line are matched and/or the production target is removed. So
suddenly, instead of a single or a few particles it becomes possible that up to around
10^9 particles per bunch might be delivered. Please evaluate the consequences for you
r
experimental apparatus and document them here.


Sin
ce we can run at full electron intensity

per pulse, we do not have a problem with
this issue.

The exper
imental setup is well away from the
ESA
electron beam.



3

Logistics

Spa
ce Requirements
:














Fig. 1
: Approximate layout of the low energy neutron beam line facility at SLAC.















Fig.
2
: LLNL LAr TPC setup including electronics and cryogenics [2].





4

(a)








(b)








Fig.
3
:
(a)
Calculated neutron detection efficiecy of EJ
-
254 scintillator for slow


neutrons.

(b) The same for EJ
-
410 scintillator.


Special Requirements (
cooling water,
gasses
, electricity,
magnets, detectors, etc):



For initial tests we need almost
nothing, only a patch panel connection to bldg 420,
where we plan to set up the electronics. Later on, during the neutron physics program, we
m
ay need a
small magnet to sweep charge
d

particles

from the
neutron
beam.

We will also
need an experimental area s
urrounded by shielding blocks, as well routine connections to
electrical power.
Additional information will be provided later.


Estimated installation time
:


Initial intallation time
is very short, b
asically 1
-
2 days to install two counter
s
, connect
them to
a
patch panel, link
them in
to a c
ounting house in bldg 420, and v
erify their
operation.


During

final test
s

with LAr

or LXe, we
probably
need
a few

weeks to

instal
l
, and 2
-
3
weeks
to run the test
.

The actual times required will depend o
n further simulations.

Duration of Test and Shift Utilization:


To measure rates initially we need 2
-
3 days

of stable running time
.

Desired Calendar dates:


Middle
-
to
-
Fall

of

2013

for initial test
s with two counters
to

verify the Fluka calculation
.
Spring 2014 for the first test with
LA
r
TPC
.