Spark Purification System

By Kemar James

NSF funded REU at Case Western Reserve UniversityAdvisor: Dr. Thomas Shutt, Dr. Dan Akerib

and Dr. Carmen Carmona

Introduction:Cosmological evidence of “Dark Matter”

To confirm its existence and thoroughly understand it to explain the our universe and its formation.

The LUX collaboration is attempting this through “direct detection” using a dual phase xenon detector.

Unfortunately due to the impurity levels, the xenon needs to be purified to make longer electron drift paths possible.

Thus allowing the nuclei recoil of the WIMP ( dark matter candidate) interaction to be detected.

The Spark Purification System

Noble Gas/Liquid

Spark Tube

Filtration System Pump

Why use a titanium electrode?

It readily reacts with O2 to form titanium oxide, thus reducing the O2 impurities in xenon/argon

It’s a good conductor, thus making it ideal for the electrode

High resistivity to corrosion

LUX Detector uses xenon noble gas/liquid

Dense and homogeneous large detector masses (crucial to explore lower cross section values).

Inert, not flammable and very good dielectrics.

High electron motilities, which allows long drift distances.

Good scintillating abilities.

Why xenon ?

Experimental Setup:

Results and Observations:

Titanium electrode Geometry

Dimensions Breakdown voltage to initialized spark (kV)In 1.5” tube

Threaded Rod 0.303’’ 6.00

Threaded Rod with grooves

0.303’’ 7.15

Modified rod

Regular rod

Results and Observations:

Titanium electrode Geometry

Dimensions (inches)

Breakdown voltage to initialize

spark s (kV) in 1’’ tube

Distance between

electrodes (inches)

Threaded Rod

0.303 3.5 0.293

0.244 4.2 0.32

Strip 0.005*0.434

3.0 0.26

0.005*0.320

3.5 0.29

0.005*0.200

3.76 0.35

Threaded rod Strip

Results and Observations:

0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

0.5

1

1.5

2

2.5

3

Distance between electrodes

Bre

akdow

n v

olt

age

The spark box breakdown voltage vs. the distance between the electrodes

Results and Observations

Results and Observations:

Voltage (kV)

Current (mA)

Sparks/ Second

1.3 2.5 2-4

1.3 3 4-8

1.3 5.4 10-15

Conclusions:The experiment was successful in generating the sparks

necessary to produce getter material (Titanium dust particles) for various electrodes geometries.

The curvature of the titanium electrode is proportional to the breakdown voltage .

The spark box without a doubt is superior, since sparks are generated at a lower voltage with the same separation between the electrodes as in the spark tube.

AcknowledgementsThis work was supported the NSF grant numbers DMR-0850037.

I would also like to acknowledge the program coordinators Kathleen Kash and Edith Gaffney.

Finally I would also like to thank my advisors Dr. Thomas Shutt , Dr. Dan Akerib, and Carmen Carmona for the tremendous work they have done to equip and guide me along this wonderful experience.

References1. Gaitskell, R. J., Direct detection of dark matter, Ann . Rev. Nucl. Part. Sci.

54(2004) 315-359.

2. Sorensen, P. F., “A Position-Sensitive Liquid Xenon Time-Projection Chamber for Direct detection of Dark Matter”. Ph.D. thesis (2008).

3. Griffiths, D. J., Introduction to Electrodynamics, Third Edition. Upper Saddle River, New Jersey: Prentice Hall , 1999.

4. Ramsey, B., Bolotnikov A., "Purification techniques and purity and density measurements of high-pressure Xe." Nucl. Inst. Meth. A 383 (1996): 619-623.

Any Questions ?

What is a Spark ? This is a type of ESD that occurs when

the electric field strength exceeds the dielectric field strength, thus ionizing the conductive channel in the gas.

This may cause a rapid increase in the number of free electrons and ions in the gas, temporarily causing the air to abruptly become an electrical conductor

At this point a sudden and momentary

electric current flows between two objects at different electrical potentials caused by direct contact or induced by an electrostatic field

Breakdown voltage in different gaseous enviroments

R8778 PMT base (d=5mm)

ObjectivesSpark Purification System

Spark Tube Identify tube and titanium electrode geometry suitable and

assemble them.

Generate continuous sparks within a localized argon gas environment and then observe how the geometry of the titanium electrode, tube size, current and voltage affects the spark rate.

Identify the dust particles generated from the sparks

Make a correlation between the duration of the sparks to the mass of particles produce and the amount required to purify “x” amount of argon to a purification level of “y”.

Filtration system

Why the use of heavy noble gases/liquids?These liquids are dense and homogeneous. This

allows to construct large detector masses. This is crucial to explore lower cross section values.

Noble gases are inert, not flammable and very good dielectrics.

Liquefied noble gases do not attach electrons, and electron mobilities are high for the heavier noble gases, which allows long drift distances.

They are bright scintillators.