Monitors Meeting
July 21, 2009
Slide 1
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Measuring Atlas Radiation Backgrounds
in the Muon System at Startup:
A U.S. ATLAS Upgrade R&D Project
Michael Shupe, Leif Shaver, Michael Starr,
Matt Adams (2007-08, undergraduate)
University of Arizona
THIS WORK IS AN ATLAS UPGRADE R&D PROJECT, FUNDED THROUGH
U.S. ATLAS.
PEOPLE: Currently, M. Shupe. Later, A. Savine. We are about to
recruit a postdoc who would work part-time on this project.
ATLAS Radiation Monitors
University of Arizona
Monitors Meeting
July 21, 2009
Slide 2
Michael Shupe
University of Arizona
Tucson, Arizona
LHC Upgrade Issues in the Muon System
Inner bore of Forward Toroid is a critical
thin spot in the current design. May need
redesign to reduce background rates
after LHC Upgrade.
Muon region
safety factors
are 2-5!
Beam pipe is a large
background source.
May need to be
changed to beryllium.
1
Monitors Meeting
July 21, 2009
Slide 3
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Aims/Scope of This Project
• Measure neutron, photon, and charged particle fluxes
and spectra in pulsed mode for sensitivity at low
luminosity. Compare measured fluxes to Fluka, GCalor,
Geant4, etc., then “retune” simulations.
Æ Reduce muon safety factors, for realistic R&D.
• Monitor sets are at the following C-End locations:
(1)
In CSC region, at small r in Small Wheel
(2)
In TGC1, at small r in Big Wheel
(3)
In TGC2, at slightly larger r
(4)
On UX15 endwall, just outside TAS shield
(5)
On UX15 sidewall, opposite USA15
• All backgrounds are mixed particle types, and broad
spectrum.
Michael Shupe
University of Arizona
Tucson, Arizona
ATLAS Radiation Monitors
University of Arizona
Monitors Meeting
July 21, 2009
Slide 4
Side Wall to USA15
Monitor
Set
Locations
End Wall
TGC2
1
CSC
TGC1
Monitors Meeting
July 21, 2009
Slide 5
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Monitor Set, Installed in TGC2 Wheel, July, 2006.
3
2
1
4
Six scintillation detectors and one boron-lined proportional tube
Monitors Meeting
July 21, 2009
Slide 6
ATLAS Radiation Monitors
University of Arizona
Monitor Types
Scintillators: crystals,
plastic wafers, or liquid
cells: 1” x 1”, coupled to
PMT’s. Some are doped
with boron or lithium for
thermal neutron detection.
Gas detectors (sealed):
proportional tubes with doped
gases or linings.
Michael Shupe
University of Arizona
Tucson, Arizona
Monitors Meeting
July 21, 2009
Slide 7
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Thermal Neutron Detectors
(1) Boron lined proportional tube: n + 10B —› 7Li + α
Li or α ionize heavily. Pulse-height discrimination
minimizes γ and MIP backgrounds.
Or, Proportional tube with BF3 gas: not as radiation
resistant as (1), but cleaner signal separation.
(2) Boron doped plastic scintillator, on PMT:
Same reaction. Run beside undoped counter of same
construction. Find n flux by subtraction.
(3) ZnS(Ag) plastic scint with 6Li: Old favorite.
Efficiencies are well defined, and
rates are easy to extract online.
Monitors Meeting
July 21, 2009
Slide 8
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Photon Spectroscopy
Atlas test beam background fluxes were measured using a BGO
crystal outside iron shielding, and were reported in 2000 by Chris
Fabjan, Edda Gschwendtner, and Helmut Vincke. They demonstrated
that mixed neutron and photon fluxes could be analyzed by convolving
simulated spectra with the scintillation detector response. Our
scintillator choices:
(1) LSO Crystal:
St. Gobain PreLude 420 (LuYSiO:Ce) crystal: high
density (like BGO), thermal stability (unlike BGO).
(2) NaI(Tl) Crystal: Will damage sooner, but well
understood.
Some spectral features can be picked out and reported online. But
full understanding of spectra requires offline analysis by
simulation and convolution—as with earlier BGO work.
Monitors Meeting
July 21, 2009
Slide 9
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Fast Neutron Detectors
Fast neutrons in hydrogenic materials scatter elastically,
producing slow recoil protons. Threshold ~ 1 MeV.
(1) Liquid Scintillator Cell, NE213:
PMT pulse-shape discrimination (PSD), is used to
separate recoil proton pulses (large slow component)
from photon and MIP pulses. PSD requires fast
waveform recorders, and is becoming more common
practice in the nuclear physics community.
(2) NaI(Tl):
PSD can be applied to these standard
scintillators as well, but the discrimination threshold
is higher—above 10 MeV.
(3) ZnS(Ag) plastic scintillator (undoped):
Sensitive to recoil protons.
As with photon spectra, this requires detailed offline analysis.
Monitors Meeting
July 21, 2009
Slide 10
Michael Shupe
University of Arizona
Tucson, Arizona
ATLAS Radiation Monitors
University of Arizona
Detector Calibration at Arizona
• All detectors calibrated with
Co60 and Cs137 gamma sources.
• First monitor set also tested
with PuBe and Cf neutron
sources at Nuclear Engineering.
• Spectra taken with cable
lengths up to 100 m, the
maximum needed for installation
in ATLAS.
LSO Spectrum
Monitors Meeting
July 21, 2009
Slide 11
ATLAS Radiation Monitors
University of Arizona
ATLAS Big Wheel at C End:
Radiation monitor sets,
TGC1 and TGC2, are near
beam in horizontal sectors,
between TGC chambers,
near the beam on the side
nearest USA15.
Michael Shupe
University of Arizona
Tucson, Arizona
Monitors Meeting
July 21, 2009
Slide 12
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Small Wheel monitors installed on surface – Bldg. 190
Same positioning as in TGC1 Æ USA15 side nearest beam.
Monitors Meeting
July 21, 2009
Slide 13
Michael Shupe
University of Arizona
Tucson, Arizona
ATLAS Radiation Monitors
University of Arizona
ATLAS DAQ: Local and Remote, Analysis and Monitoring
Cavern
USA15
Monitor
Set 1
e.g. NaI, ZnS,
LSO, 10B prop
tube, ion
chamber, etc.
MUX
Set 2 (8)
Set 3 (8)
Set N (8)
64
input
DMX
2
outpt
MCA
DAQ PC
5ns,12bit,32Ms
64 Channel
Discriminate
& Scale
atlasgw
Gain and shaping for pulse height analysis
are computer controllable.
Michael Shupe
University of Arizona
Tucson, Arizona
ATLAS Radiation Monitors
University of Arizona
Monitors Meeting
July 21, 2009
Slide 14
Fluxes, and Sensor Counting Rates
Fluxes in KHz/cm2 at luminosity 1034:
n,therm
n,fast
40.6
38.1
31.8
0.74
7.3
TGC1 Region
3.2
1.7
15.8
.061
.59
TAS region
1.5
1.3
1.82
.023
.078
CSC Region
γ<10MeV γ>10MeV
h>10MeV
EG: 10B lined proportional tube with A = 70 cm2, ε = .001, operating
at a luminosity of 1033, counting thermal neutrons, with pulse height
discrimination against other backgrounds:
CSC: 284 Hz
TGC1 : 22.4 Hz
Endwall: 10-20 Hz
Looks reasonable. We are applying this analysis to all sensors.
Monitors Meeting
July 21, 2009
Slide 15
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Operating Modes
(1) “Instantaneous” Rates
Doped detector raw rates above a threshold.
Can be converted to instantaneous flux and sent to Control Room.
(2) “Fast Turn-Around” Rates
Spectrum features that can be fit above a background, and
used to extract instantaneous flux.
Can be sent to Control Room, less frequently than (1).
(2) Offline Analysis
Full spectra are sent to Arizona, and elsewhere, for offline
analysis using simulation and convolution to separate mixed
backgrounds.
Æ These would be used, in turn, to reweight the simulations and
reduce the safety factors, making the upgrade simulations
more precise. This is, in effect, a “test beam run” done in
situ. (MPX detectors also have this capability.)
Monitors Meeting
July 21, 2009
Slide 16
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Status
• The AZ RadMon DAQ system is cycling through all
scintillation detectors taking spectra with various
gains and running times. UX15 is one of the leastradioactive places on Earth at the moment, so these
are exceptionally dull. We’ll see if there is any
identifiable activity coming from the special concrete
behind the wall-mounted detectors.
• The proportional tubes will be set up soon.
Monitors Meeting
July 21, 2009
Slide 17
ATLAS Radiation Monitors
University of Arizona
Michael Shupe
University of Arizona
Tucson, Arizona
Internet Access Mode?
The DAQ computer is connected to the P1 internet, and
at present we are accessing it in “expert” mode to allow
for remote software development and commissioning.
This status will be revoked as LHC operation nears. At
that point we will need a robotic interface (GUI or script)
to atlasgw.cern.ch that allows for specification of all
run conditions, and controls the outflow of data to the
C.R. and elsewhere.
It would be preferable to continue to have remote access
to the DAQ computer. Is it possible to put it only on the
public internet in P1, and then have a robotic process
running on lxplus to feed data to the C.R. through a much
simplified atlasgw interface?