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 ElectroproductionA high-energy electron beam releases a

photon of a very high frequency. The high-frequency 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 PionsWe 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.

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.

T. Horn et al., Phys. Rev. Lett. 97 (2006) 192001.

T. Horn et al., arXiv:0707.1794 (2007).

A.P. Bakulev et al, Phys. Rev. D70 (2004)]

Kaon Aerogel Detector•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. Kaon

Cherenkov Light

PMTs

Aerogel Panels

Front View

Side View

Aerogel Tests

•Several Properties need to be looked at

•Measurements to verify Index of Refraction

•Experiments to test light output, signal strength, etc.

Aerogel Tests (cont.)

Setup diagram

Light box

•Aerogel Properties Tested using cosmic muons.

•Test setup must be light-tight.

•Setup Constructed Here at CUA

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

User == DAQ

VME

DATA EQUIP.

ADC

DAQ Setup

CAMAC

[various modules, etc.]

1500

TI

CAMAC Interface

CPU

Crate Controller

Ethernet

DB9

CODA 2.6

Data Acquisition

PMT Uniformity Tests● Large Diameter PMTs may

perhaps output varying signals dependnig on area of photocathode struck with light.

● Necessary to investigate Uniformity

● LED attached to a two-axis 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.