Calibration

SNO+ Light Injec0on Calibra0on System: a concept for CHIPS? Jeff Hartnell University of Sussex May 2013 Credit for the work presented here should not be attributed to me but any
mistakes are my own.
A lot of development was done by Simon Peeters’s group at Sussex in
collaboration with Leeds, Lisbon, Oxford, QMUL and other SNO+ groups.
SNO+ system built on work done for MINOS and Double Chooz.
Jeff Hartnell, May '13 2 SNO+ Detector Acrylic vessel (AV) 12 m diameter 780 tonnes of LAB LS 1700 tonnes H20 inner shielding 5700 tonnes H20 outer shielding ~30m
~9500 PMTs PMT support structure ~18 m diameter National Geographic
Jeff Hartnell, May '13 3 ELLIE
AMELLIE – Monitor the attenuation within the
detector volume. Using wide angle quartz fibres.
●
SMELLIE – Monitors the scattering within the
AV. Using 12 collimated beams of different
wavelengths, pointing in 3 different directions
from 4 locations.
●
TELLIE – Monitor the timing (T0 and time walk)
and gain calibration of the PMTs. Using PMMA
fibres mounted at each of the 91 PSUP nodes, 1
neck mounted.
●
Jeff Hartnell, May '13 4 J Sinclair
TELLIE calibra0on aims •  Reduce the 0ming offsets between PMTs to be smaller than the intrinsic ji^er PMT ji^er of 1.6ns (and decay 0me of WLS scint. signal of ~6ns) –  Target is to reduce 0ming offsets to <1ns –  Also measure the 0me walk •  Miscalibra0ons impact on posi0on and charge reconstruc0on Jeff Hartnell, May '13 5 92 leds each w/ own electronic driver board ~50 m of fibre op0c cable for each of 92 injec0on points Feed-through
box for fibers
LED rack
Calibration clean
room
Bundle with
all fibers
AV
hold-up
ropes
PSUP
hold-up
ropes
injec0on point: one LED illuminates each fibre, light then shines 18m across detector Opening angle of injected light is 14.5 degrees in water (from centre to 20% of max. intensity) fiber
termination
support
Jeff Hartnell, May '13 AV
hold-down
ropes
6 468
469
470
Blue spot shows PMTs hit by 1 injec0on point (of 92) The results of this simulation can be visualized using the SNO+ viewer. In Figure 14 only the
flattened "icosahedral" map as well as the timing histogram are shown for one event.
Figure 14. Viewer screenshot for one event without scattering or absorption injected with an 11 degree
tophat beam.
471
472
473
474
475
Pattern/number of injection points chosen so that each PMT
is illuminated by >2 leds (some by 3 or 4).
There are several
interesting
in Figure
14 which
may warrant
discussion.
Timing
offsets features
between
each led
are reduced
by design
as The combination of the hit much
PMT map
the hitand
timeresiduals
spectrum provide
into thein
reflection
as with
possible
will beinsight
determined
a fit: processes.
The first time peak
aroundis200
nsconstrained.
(in purple) creates a small spot which is reflected from the AV
system
over
and hits the PMTs
immediately planned
surrounding
the injection
pointlaserball
itself. Theinsecond
Cross-check
using
a deployed
centrepeak (in blue)
Jeff Hartnell, May '13 around 280 ns is the light which has travelled
through the detector and creates the visible spot.
7 New innova0on for SNO+ Hole drilled in LED
Fibre glued in hole
160
per pulse is less than a nanosecond (FWHM) after the full length of 47.75
the very brightest pulses of more of 106 photons arriving at the end of th
width rises to 8 ns.
161
3. Fibre Characterisation
162
3.1 Requirements and Specifications
158
End of fibre sits right
above the little piece
of semiconductor
that produces the
light
159
163
164
Collect more of the
light into the fibre
like this, time
spectrum not
altered.
(don’t have
numbers)
165
166
167
168
The optical fibre cables chosen are Mitsubishi Rayon PMMA fibres [4]. T
ensuring an automatic redundancy at each injection point without multiplyi
to install and with better mechanical robutness. Their 1 mm diameter and l
(0.5) guarantees a wide illumination area. The dry-ends are two pre-mounte
the wet-end is a duplex connector to be inserted in the mounting plate.
fibres have the same length, leaving the propagation delay constant in the e
169
170
171
172
173
In practice there are 91 nodes in which fibers can be installed poiti
centre of the detector. The attenuation, aperture angle and timing distortion
characterized, and quality control of 110 double fibre cables, kept record o
order to select the best ones and keep track of small variations within the s
174
3.2 Emission
Profile
Figure 3. Drilled
LED with
mounted optical fibre
A specific setup was built to study the emission properties of the duplex
176
moving in front of a fixed fibre and shown schematically in figure 5. A L
177
final one (see section 2) injects light into a patch cable, then into the full le
178
the connections of the final system. The PMT is a mini 8 Ha
Jeff Hartnell, M
ay reproducing
'13 175
124
125
the output.
Various wavelengths
available, e.g. 435 nm
2
8 electronic driver circuits per box Figure 13. One of the twelve boxes of the electronics of the ligh calibration system. The eight small boards
are the LED drivers. The LED is encapsulated in the brass cones and not visible. The eight patch optical
cables are fixed onto the back panel for connection with the dry end of the 45 m fibres.
Jeff Hartnell, May '13 9 Fast electronic driver circuits Fibre dispersion is
~3.5 ns over ~50 m
Light output at the
far end of the fibre
is controlled and
has a range of
about 1000 to
1,000,000 photons
0.012
intensity (a.u.)
FWHM of pulse is
~6 ns
incidence angles in water
0 deg
11 deg
0.01
0.008
0.006
0.004
0.002
0
5
10
15
20
25
time (ns)
Figure 6. Time distribution of the light pulses emitted by the LED driver and going through the full length
optical fibre, at the central position and at an angle corresponding to 11 in water. The time offset is common
to both histograms, and both are normalised to their integrals.
30 Jeff Hartnell, May '13 Hz)
ee)
Angular Distribution in Water
10 Costs •  Likely to be dominated by people’s 0me (student & postdoc & electronics engineer). •  Hardware for SNO+ cost: my personal guess is of order many-­‐£10k. Jeff Hartnell, May '13 11 Conclusions •  Broad-­‐brush light injec0on calibra0on concept used for SNO+ may be applicable for CHIPS •  For the SNO+ 0ming and gain calibra0on: –  Inject fast, 6ns FWHM, pulses of light using leds coupled to 50m long fibre op0c cables –  Light is directed across the detector to illuminate PMTs on the opposite side to where light was injected –  SNO+ system can deliver controlled pulses of light with a range of intensity between 1000 and 1,000,000 photons to the far end of the fibre op0c cable Jeff Hartnell, May '13 12 Backup slides Jeff Hartnell, May '13 13