Transcript Data acquisition techniques and development of testing equipment

Data acquisition techniques and
development of testing equipment
for the JLab Hall C 12 GeV kaon
aerogel detector
Nathaniel Hlavin, Mike Metz
VSL Presentation
19 August 2011
Outline
●
Brief Physics Motivation
●
Data AcQuisition (DAQ) System
●
●
●
●
Key component used for all tests
Aerogel testing
Large diameter photomultiplier tube (PMT)
uniformity tests
PMT gain tests
Physical Motivation:
Proton Substructure
To understand further what makes up a proton, we use
Generalized Parton Distributions (GPD).
They combine the spatial and momentum distribution of the quarks
into one concise chart. Below are some examples based on
models. We seek experimental confirmation. “x” is the fraction of
the momentum of the quark over the momentum of the proton
Meson Electroproduction
A high-energy electron beam releases a
photon of a very high frequency. The highfrequency allows us to observe objects with
greater detail.
The interaction of the photon and proton
(pictured “GPD” here) results in a neutron
(pictured here with momentum p’) and a
meson (for example a pion or a kaon). For
our proposed experiment, the meson would
be a kaon.
We are able to detect/calculate the portions of
the diagram above to dotted line, and from
them we can contsruct the GPD. However,
the meson released must conform with the
Quantum Chromo Dynamic (QCD) theory of
quarks.
K+ or
Above dotted
Line: Hard
Scattering
Process (QCD)
We can calculate
this.
Below Dotted
Line: GPD.
This is what we
want.
Problematic Pions
We know how to calculate the
hard or perturbative QCD
model, but our data for the
pion spatial quark distribution
does not match the QCD
prediction.
T. Horn et al., Phys. Rev. Lett. 97 (2006) 192001.
T. Horn et al., arXiv:0707.1794 (2007).
Further experimentation with the
kaon could provide data that
matches the QCD prediction.
The dotted prediction seems to
doubt it.
Matching data would enable
GPD construction to reveal the
proton substructure.
The 12 GeV upgrade allows for
kaon production above a Q2
value of 1, and even higher
into the hard QCD range.
A.P. Bakulev et al, Phys. Rev. D70 (2004)]
Kaon Aerogel Detector
Front View
•As a charged particle (kaon) passes through a
substance (aerogel) faster than light passes through
that substance, light is emitted.
•This light is called Cherenkov light and can be
thought of as a shock wave in the electromagnetic
field. It is analogous to a sonic boom.
•The light is collected by Photomultiplier Tubes
(PMT) and converted into an electron signal by the
photoelectric effect.
•This signal is then amplified into a signal that can
be analyzed.
•An example image of a detector is pictured at right.
Cherenkov Light
Side View
Aerogel
Panels
PMTs
Kaon
Aerogel Tests
•Several Properties need to be
looked at
•Measurements to verify Index of
Refraction
•Experiments to test light output,
signal strength, etc.
•Aerogel Properties Tested using
cosmic muons.
•Test setup must be light-tight.
•Setup Constructed Here at CUA
Aerogel
Tests (cont.)
Setup diagram
Light box
Electronics Diagram
(Aerogel Testing)
Aerogel Tests (cont.)
Data Acquisition
•Uses CODA 2.6.1 Software.
•Runs on Scientific Linux CentOS 5.5
•Interfaces with VME crate that boots from
computer with Power PC VxWorks OS.
•Connected to equipment/modules in CAMAC
crate
•Data analyzed by ROOT programs.
•Software and some hardware acquired from JLab
CODA 2.6
DAQ Setup
User == DAQ
DATA EQUIP.
DB9
ADC
Ethernet
CAMAC
1500
Crate Controller
[various modules, etc.]
CPU
VME
TI
CAMAC
Interface
Data Acquisition
●
●
●
●
●
Large Diameter PMTs
may perhaps output
varying signals
dependnig on area of
photocathode struck
with light.
PMT Uniformity
Tests
Necessary to
investigate Uniformity
LED attached to a twoaxis stepper motor
setup
Scans 10x10 grid and
measures gain at each
point
Thanks to Jack Segal
at JLab for technical
support
Uniformity test setup
PMT Uniformity Tests (cont.)
Data analysis application
PMT Gain Testing
•Pulsing LED Used to test PMT Gain
•Gain: Amount of electrons output by PMT when
single electron is emitted from photocathode
window.
•The “multiplier” in photomultiplier tube.
PMT Gain tests
●
Data analysis software ROOT used to fit curves to the data
–
–
Pedestal: trigger signals without PMT signal
Single-electron peak: charge output by the PMT when a single photoelectron is
released
Gain vs. HV
Outlook
•PMT and Aerogel
Characterization to
continue
•~70 PMTs to test and
~200 L Aerogel
•Detector Construction
to begin at CUA
•Upcoming Use in
approved JLab
experiment E12-09-011
Acknowledgements
•Thanks to Dr. Horn for her tireless support and
mentorship
•JLab staff: Dr. Hamlet Mkrtchyan, Dr. Vardan
Tadevosyan, Dr. David Abbott, Dr. Jack Segal, Dr
Ibrahim Albayrak
•VSL for technical support and hardware.
•CUA for the opportunity to conduct research.