Production of Negative Production of Negative Hydrogen ionsHydrogen ions

Xavier Hailey Xavier Hailey

University of Illinois at ChicagoUniversity of Illinois at Chicago

Supervisor: Doug Moehs Supervisor: Doug Moehs

Fermi National Accelerator Laboratory Fermi National Accelerator Laboratory

2003 SIST summer program2003 SIST summer program

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f• IntroductionIntroduction - Cockroft-Walton - Cockroft-Walton

- Purpose- Purpose

• Basic PrinciplesBasic Principles- H- ions source- H- ions source- Flow Systems & Electrical - Flow Systems & Electrical Circuit Circuit

• ExperimentsExperiments- Preliminary Experiment- Preliminary Experiment

- Seal Source Experiment- Seal Source Experiment

• ConclusionConclusion

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f-- Housing for the creations Housing for the creations

of H- ions and used to of H- ions and used to accelerating H- ions to accelerating H- ions to energy levels of 750 keVenergy levels of 750 keV..

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f-- To increase the efficiency of To increase the efficiency of

the magnetron ion source by the magnetron ion source by decreasing the leakage decreasing the leakage amount of background gas.amount of background gas.

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• MagnetronMagnetronA surface-plasma ion source A surface-plasma ion source that produces H- ions by that produces H- ions by surface interactions with surface interactions with energetic plasma.energetic plasma.

H- ions are created by the H- ions are created by the absorption and reflection of absorption and reflection of hydrogen gas upon the hydrogen gas upon the cathode surface.cathode surface.

f• Flow SystemFlow System

- One important property is call - One important property is call ConductanceConductance

- - ConductanceConductance -- The amount of flow at a specific pressure that crosses a given The amount of flow at a specific pressure that crosses a given

area of area of pressure.pressure. -- Geometrically determine by the flow channel. Geometrically determine by the flow channel.

- Mathematical Representation: - Mathematical Representation: C = Q / C = Q / ∆P∆P , ,

where C is conductance, Q is throughput, and where C is conductance, Q is throughput, and ∆P∆P is pressure is pressure gradientgradient

- SI unit are - SI unit are mm33/s/s

f• Flow SystemFlow System

- - ThroughputThroughput -- Proportionally related to the volume metric flow rate by, Proportionally related to the volume metric flow rate by,

Q=P Q=P •• FFwhere P is pressure and F is volumetric flow ratewhere P is pressure and F is volumetric flow rate

- Assuming that P is one atmosphere, Q approximates to F and- Assuming that P is one atmosphere, Q approximates to F and

C C F / F / ∆P∆P

fFlow SystemFlow System

- Conductance C- Conductance C

- Throughput Q- Throughput Q

- Pressure Gradient - Pressure Gradient PP

C = Q / C = Q / PP

Electrical CircuitElectrical Circuit

- Resistance R- Resistance R

- Current I- Current I

- Potential Difference V- Potential Difference V

1 / R = I / V1 / R = I / V

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f• PurposePurpose

- - To determine the ratioTo determine the ratio C CLL/C/CE E

by forcing all the nitrogen gas by forcing all the nitrogen gas to flow through the leaks of to flow through the leaks of the source.the source.

V1 = I (RV1 = I (RLL+R+REE) V2=IR) V2=IRLL

(R(RL L + R+ REE) = V1/I) = V1/I RRLL = V2 / I = V2 / I

A

V1

V2

RLRE

A

RE RL

V1

V2

Flow Flow metermeter

P1

H- ion source

P2

N2 input

f• SlopesSlopes

P1(gauge) is 1.7085P1(gauge) is 1.7085P2(gauge) is 1.5765P2(gauge) is 1.5765

(R(RL L + R+ REE) = 1.7085 ) = 1.7085

RRLL = 1.5765 = 1.5765

RREE = 0.132 = 0.132

• RatioRatioR R C C-1-1= = P/FP/F

RREE/R/RLL CCLL/C/CE E = (0.132/1.5765)= (0.132/1.5765)

8 %8 %

Pressure vs. Flow of Nitrogen

y = 1.7085x

y = 1.5765x

0

10

20

30

40

50

60

0 10 20 30 40Flow (SCFH)

Pres

sure

(mm

Hg)

P 1(gauge)

P 2(gauge)

Linear(P 1(gauge) )

Linear(P 2(gauge) )

f• Under normal conditions, an unseal source operates at a Under normal conditions, an unseal source operates at a

pressure of 40 mTorr has a current output of 60 mA.pressure of 40 mTorr has a current output of 60 mA.

• Introducing seal source should increase the current output Introducing seal source should increase the current output since the majority of the gas would exit the exhaust slit.since the majority of the gas would exit the exhaust slit.

• Decreasing the pressure should display a higher current Decreasing the pressure should display a higher current output than the unsealed source if leakage amount was output than the unsealed source if leakage amount was significant.significant.

f• Preliminary ExperimentPreliminary Experiment

- Showed that approximately 8% of the gas leaks from the source- Showed that approximately 8% of the gas leaks from the source

• Seal Source ExperimentSeal Source Experiment- Decreasing the source pressure showed a significant decrease in the - Decreasing the source pressure showed a significant decrease in the current outputcurrent output

Hence, further tests are necessary to concluded that the Hence, further tests are necessary to concluded that the leakage leakage

amount plays no major part in the production of negative amount plays no major part in the production of negative hydrogen ion.hydrogen ion.

f• Special thanks to:Special thanks to:

Charles SchmidtCharles Schmidt

Dough MoehsDough Moehs

James WendtJames Wendt

Ray HernRay Hern