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High Current Density and High Brightness H - Sources for Accelerators. Vadim Dudnikov Brookhaven Technology Group, Inc. FNAL, December 2005. ACKNOWLEDGMENTS .

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High current density and high brightness h sources for accelerators

High Current Density and High Brightness H- Sources for Accelerators

Vadim Dudnikov

Brookhaven Technology Group, Inc.

FNAL, December 2005


Acknowledgments
ACKNOWLEDGMENTS

I am very grateful to the ISIS Team for choosing Charge Exchange Injection and Penning SPS for ISIS operation and for successful demonstration of it’s high performance in real accelerator operation.



Abstract
Abstract

  • Operation Experience of Compact Surface-Plasma Sources (CSPS) under operation in different laboratories around the world, will be considered.

  • Features of CSPS are small volume, small gaps between electrodes, high plasma density and high emission current density and high brightness, high pulsed gas efficiency and low electron current.

  • In many versions of CSPS were reached very long operation time.

  • Features of CSPS important for long time operation will be considered.


Contents

  • Introduction.

  • Historical remarks.

  • Negative ion production in surface- plasma interaction.

  • Cesium catalysis.

  • Surface Plasma Sources- SPS.

  • Charge-exchange cooling. Electron suppression.

  • Beam extraction, formation, transportation.

  • Space charge neutralization. Instability damping.

  • SPS design. Gas pulser, cesium control, cooling.

  • SPS life time. SPS in accelerators.

  • Further development.

  • Summary.

  • Acknowledgment.


Horst klein 20 icfa workshop summary
Horst Klein (20 ICFA Workshop summary).

“The ion sources, and especially the H- sources, are still somewhat a black magic. Therefore intense theoretical and experimental work has to be performed in different labs to achieve the new requirements. In Europe the Negative Ion Source network, supported by the European Union, with its 8 partners will help to reach the goal. But also such a meeting as we have had in Femilab is very helpful and intensifies the worldwide collaboration. Concerning the different types of ion sources, I think the most promising candidates for H- are the Penning ion source and the volume source (Large Volume SPS). The ECR source may be a hope for the future”.

Intuition and hand experience are important components for H- sources development.


H beam brightness in different sps r welton sns
H- beam brightness in different SPS ( R.Welton, SNS).

Beam brightness and pulse current of operational ion sources (points) and new facility requirements (rectangles)Magnetron sources: 1-DESY, 2-BNL, 3-ANL, 4-FNAL. Multicusp RF sources: 5-DESY, 6-SSC; Penning sources: 7-RAL and 8-INR;. Multicusp surface conversion sources: 9-KEK and 10 –LANL Multicusp filament sources: 11-TRIUMF and 12-Jyvaskyla.


Ion source requirements for new accelerators projects from r scrivens review
Ion Source requirements for new accelerators projects ( from R. Scrivens review)

Ion Source parameters required for selected high power project. 1rms, normalized, in mm mrad


Huashung zhang ion sources springer 1999 p 326
HUASHUNG ZHANG, ION SOURCES,Springer, 1999. p.326

  • Based on the achievements of positive ion sources, H- ion sources have

    been developed in two ways:

  • 1) Negative ions are extracted from the plasma of positive ion sources. Before the 1970's, the H- current was limited to less than 5 mA. This is because in a general high temperature plasma (Te ~> 10 eV) the H- formation cross section(~10-18 cm2 ) is 3 to 4 orders less than the H- destruction cross sections (~2 to 7x10-14 cm2).

  • In 1962, Krohn [7] discovered that the yield of sputtered negative ions increased by one order while Cs+ ions impacted the metal target.

  • Unfortunately, this result was not immediately used to develop a NIS up to 1970. An H- surface plasma source (SPS) was invented by introducing cesium into the hydrogen discharge plasma at 1971.

  • It quickly led to increasing the H- current to several Amperes. Also the cesium sputter NISs were rapidly developed.

  • Since discovering, at the end of the 1970’s, that the dissociative attachment cross section of highly vibrationally excited H2-molecules in a low-temperature plasma is higher by 104-105 than the groundstate[8,9], high-intensity volume H- ion sources have been developed.

  • At the end of the 1980's, H- volume ion sources combined with cesium has evolved with domination of surface- plasma generation of negative ions.


Adsorption of alkaline metals significantly increases the secondary emission of negative ions
Adsorption of alkaline metals significantly increases the secondary emission of negative ions

  • In 1961, by Ahmet Ayukhanov (Tashkent Electronics Institute) was observed that the adsorption of alkaline metals significantly increases the secondary emission of negative ions. A little later the investigations of this effect were presented by Krohn (Argonne Nat. Lab.). However, even with the presence of cesium on the surface the intensity of beams of negative ions obtained by the secondary emission did not exceed the microampere level.

  • These results became the basis of secondary-emission sputtering negative ion sources with a microampere level intensity for tandem accelerators.

  • A. Ayukhanov, PhD. Thesis, Secondary emission of negative ions with bombardment by alkali positive ions. 1961.

  • U. A. Arifov, and A. Kh. Ayukhanov, Izvestiya AN Uzbek. SSR, Ser.

    Fiz. Mat. Nauk. No. 6, 34 (1961).

  • in book U. A. Arifov, Interactions of Atomic Particles with a Solid (Nauka, Moscow, 1986).

  • V. E. Krohn, J. Appl. Phys. 33, 3523 (1962).


Budker institute of nuclear physics www inp nsk su
Budker Institute of Nuclear Physics secondary emission of negative ionswww.inp.nsk.su


History of secondary emission of negative ions

Surface Plasma Sources Development

(J.Peters, RSI, v.71, 2000)

Cesium Catalysis:

“Enhancement of negative ion production by admixture into discharge a substance with a low ionization potential, such as cesium”.



H-/D- LV SPS for Tokomac Neutral Beam Injectors Catalysis.

~$0A, ~1 MeV, 1000s,…

~1 Billion $


History of charge exchange injection rees isis icfa workshop
History of Charge Exchange Injection Catalysis.(Rees, ISIS , ICFA Workshop)

1. 1951 Alvarez, LBL (H-) ;

1956 Moon, Birmingham Un. (H+2)

2. 1962-66 Budker, Dimov, Dudnikov, Novosibirsk ;

first achievements;discovery of e-p instability.IPM

3. 1968-70 Ron Martin, ANL ; 50 MeV injection at ZGS

4. 1972 Jim Simpson, ANL ; 50-200 MeV, 30 Hz booster

5. 1975-76 Ron Martin et al, ANL ; 6 1012 ppp

6. 1977 Rauchas et al, ANL ; IPNS 50-500 MeV, 30 Hz

7. 1978 Hojvat et al, FNAL ; 0.2-8 GeV, 15 Hz booster

8. 1982 Barton et al, BNL ; 0.2-29 GeV, AGS

9. 1984 First very high intensity rings ; PSR and ISIS

10. 1980,85,88 IHEP, KEK booster, DESY III (HERA)

11. 1985-90 EHF, AHF and KAON design studies. SSC

12. 1992 AGS 1.2 GeV booster injector

13. 1990's ESS, JHF and SNS 4-5 MW sources


INP Novosibirsk, 1965, bunched beam Catalysis.

Other INP PSR 1967:

coasting

beam instability

suppressed by

increasing beam

current;

fast accumulation of

secondary plasma

is essential for

stabilization;

1.8x1012 in 6 m

first observation of an e- driven instability?

coherent betatron oscillations & beam loss

with bunched proton beam; threshold~1-1.5x1010,

circumference 2.5 m, stabilized by feedback

(G. Budker, G. Dimov, V. Dudnikov, 1965).

F. Zimmermann

V. Dudnikov, PAC2001,

PAC2005


Cs PATENT Catalysis.V. Dudnikov, The Method for Negative Ion Production, SU Author Certificate, C1.H013/04, No. 411542, Application filed at 10 March, 1972, granted 21 Sept,1973, published Bul. No 2, 15 Jan.1974.

“Enhancement of negative ion production by admixture into discharge a substance with a low ionization potential, such as cesium”.



Sps for accelerators was developed in cooperation with g derevyankin
SPS for Accelerators was developed in cooperation with V.Dudnikov,and Yu.BelchenkoG. Derevyankin


History of Volume Sources Development V.Dudnikov,and Yu.Belchenko

(J.Peters, RSI, v.71, 2000)

Blue frame is separate Surface Plasma dominated H- formation

Development of Volume Sources is finished by conversion into Large Volume SPS.


Marthe bacal fourth iaea technical meeting on negative ion based neutral beam injectors 9 may 2005
Marthe Bacal V.Dudnikov,and Yu.BelchenkoFourth IAEA Technical Meeting on “Negative Ion Based Neutral Beam Injectors”9 May 2005

  • “What ion source for volume production ??

  • New ion sources were proposed for making use of the volume production mechanism. The magnetic multipole, used in 1976 in our first experiments (Nicolopoulou et al, J. Phys. 1977) was modified by the addition of a magnetic filter. This seemed to solve the problem of H- destruction by fast electrons, since they were eliminated from the extraction chamber.

  • However, this solution was only partial, for two reasons :

  • * the negative ions may not be formed in the extraction chamber, but in the driver, near the filaments ;

  • * the magnetic multipole is very efficient to dissociate molecules, but H atoms destroy H- and H2(v) !

  • When cesium was introduced in the magnetically filtered multipole , it appeared as a suitable source for producing atoms and positive ions for surface production. Obviously, this device is not suitable for volume production !! It is really a good Large Volume Surface Plasma Source, not a Volume Source.”


General Diagram of the Surface-Plasma Mechanism V.Dudnikov,and Yu.Belchenko

for Production of Negative Ions in a Gas Discharge

Surface plasma generation of H- on anode often is a dominant process of H- formation in discharges without Cs, as well with Cs


Schematic Diagrams of Surface Plasma Sources V.Dudnikov,and Yu.Belchenko

(a) planotron (magnetron) flat cathode

(b) planotron geometrical focusing (cylindrical and spherical)

(c) Penning discharge SPS (Dudnikov type SPS)

(d) semiplanotron

(e) hollow cathode discharge SPS with independent emitter

(f) large volume SPS with filament discharge and based emitter

(g) large volume SPS with anode negative ion production

(h) large volume SPS with RF plasma production and emitter

1- anode 6- hollow cathode

2- cold cathode emitter 7- filaments

3- extractor with 8- multicusp magnetic

magnetic system wall

4- ion beam 9- RF coil

5- biased emitter 10- magnetic filter



Schematic of negative ion formation on the surface michail kishinevsky sov phys tech phys 45 1975
Schematic of negative ion formation (cesium coverage) on the surfaceMichail Kishinevsky, Sov. Phys. Tech. Phys, 45 (1975)



Enhancing surface ionization and beam formation in volume-type H- ion sourcesR.F.Welton, M.P.Stockli, M.Forrette, C.Williams, R.Keller, R.W.Thomae, EPAC 2002, Paris.

  • “Cleary, once again Cs must reside on the surface for the vast majority of its lifetime in the source and therefore surface ionization must account for the observed enhancement of H- yield.

  • In these cases, the term ‘volume ion source’ is misleading since, most of the H- results from surface, rather than volume ionization processes. Therefore, ion source design, careful consideration should be granted the interior surfaces of the source”.

  • Correct classification of ion sources is important, because it should determine a direction of devices optimization: to optimize a volume production, or surface-plasma production. Incorrect speculation of main mechanism of negative ion generation was reason of long time delay in improving of beam parameters.


First version of Planotron (Plain Magnetron) SPS, INP, 1972,

Beam current up to 230 mA, 1.5x10 mm2 , J=1.5 A/cm2 with Cs


H energy spectra from planotron
H- energy spectra from planotron

The ion spectra from a planotron usually have two peaks separated by a valley. The location of the first peak coincides with the energy eUex imparted to the negative ions by the extraction voltage. The ion energy of the second peak is higher than that of the first peak by an amount close to eUd. The oscillograms in the upper part of illustrate the change in the spectra, as a result of increasing the discharge voltage Ud from 120 V ( l ) to 210 V (4) by reducing the cesium supply. The oscillograms (1-4) in the lower part of Figureillustrated how the spectra vary as a result of increasing the hydrogen supply to the discharge chamber


Cross sections of Planotron (Magnetron) SPS of second generation: 3.7 A/cm2 with Cs (0.75 A/cm2 without Cs)


H current density from planotron with cs 3 7a cm 2 and without cs 0 75 a cm 2 inp novosibirsk 1972
H- current density from planotron with Cs (3.7A/cm generation: 3.7 A/cm2) and without Cs (0.75 A/cm2), INP, Novosibirsk, 1972


Schematic of semiplanotron sps
Schematic of semiplanotron SPS generation: 3.7 A/cm

1- emission aperture;

2- anode;

3- cathode;

4- cathode insulator;

5- discharge channal;

6- extractor;

7- magnet with magnetic insertions.


Beam current vs an arc current for different slit geometry in the semiplanotron
Beam Current vs an Arc Current for Different Slit Geometry in the Semiplanotron

Dependences of the Н- ion beam current on the discharge current have the N-shaped form with three sections: linear growth at small discharge currents, saturation or a falling section at medium currents, and linear, but slow growth at the high currents.


Cross section through lanl version of sps with penning discharge
Cross section through LANL version of in the SemiplanotronSPS WITH Penning Discharge.

Beamlet images at pepper-pot scinti1lator (noiseless discharge). Emission slit 0.5x10 mm2.

Vertical: Y Plane

Horizontal: X Plane





Review of Scientifi Instruments, operationMarch 2002, Volume 73, Issue 3, pp. 1157-1160Investigation of the mechanism of current density increase in volume sources of hydrogen negative ions at cesium adding

  • V.P. Goretsky, A.V.Ryabtsev, I.A. Soloshenko, A.F. Tarasenko, A.I. Shchedrin

    Institute of Physics of National Academy of Sciences of Ukraine, 46 prospect Nauki, Kiev 03650, Ukraine

  • In the present article the influence of adding cesium into the volume and on the surface of an ion source on its emission characteristics is studied both theoretically and experimentally. It is shown that cesium in the volume at conditions of a real ion source brings in a significant contribution to kinetic processes, but weakly influences the current of H– ions extracted from the source. It is shown both theoretically and experimentally that an observed increase of the current of H– ions with cesium added is due to the conversion of fast particles at the anode surface.

  • Thus, on the basis of experimental results and calculations it can be stated that cesium in a volume of the source under study can not lead to the increase of current H- ions. Observed growth of this current with cesium introduction is due to conversion of hydrogen atom at discharge anode surface, covered by cesium. In other words, cesium adding results in the transformation of the source of H- ions of volume type to the source of surface-plasma type.

  • Yu.Belchenko,G.Dimov, V.Dudnikov, Nucl.Fusion, 14, 113 (1974)


Operation of Dudnikov type Penning source with LaB6 cathodesK.N. Leung, G.J. DeVries, K.W. Ehlers, L.T. Jackson, J.W.Stearns, and M.D. Williams (LBL)M.G. McHarg, D.P. Ball, and W.T. Lewis (AFWL)P.W. Allison (LAML)

The Dudnikov type Penning source has been operated successfully with low work function LaB6 cathodes in a cesium-free discharge. It is found that the extracted H– current density is comparable to that of the cesium-mode operation and H– current density of 350 mA/cm2 have been obtained for an arc current of 55 A. Discharge current as high as 100 A has also been achieved for short pulse durations. The H– yield is closely related to the source geometry and the applied magnetic field. Experimental results demonstrate that the majority of the H– ions extracted are formed by volume processes in this type of source operation.

Review of Scientific Instruments -- February 1987 -- Volume 58, Issue 2, pp. 235-239


H cathodes- Detachment by Collisions with Various Particles

and Resonance Charge-Exchange Cooling

Resonance charge -exchange cooling


Cesium escaping from a pulsed discharge in sps
Cesium escaping from a pulsed discharge in SPS cathodes

there is a strong suppression of the gas and cesium flow from the emission slit by the high density plasma of the discharge.


Gas trapping by discharge in csps
Gas trapping by discharge in CSPS cathodes

  • qo-gas flux without discharge

  • qp- gas flux with discharge

  • Id- discharge current


H cathodes- Beam Intensity of SPS

Years

Beam intensity vs discharge current

for first version of semiplanotron 1976

Evolution of H- beam intensity in ISIS


Emittance, Brightness, Ion Temperature cathodes

δ

y

Emission slit

l

Emittance

Normalized emittance

x

Δx

Normalized brightness

Δα

Half spreads of energy of the

transverse motion of ions

Reduced to the plasma emission slit

Characteristics of quality of the beam formation:


Discharge Stability and Noise cathodes

n,1016 cm-3

noiseless

Diagram of discharge stability in coordinates of magnetic field B and gas density n

no discharge

n*

noisy

Bmin

B, kG

μ = eν/m (ν2 + ω2)

μ

noiseless

The effective transverse electron

mobility μ vs effective scattering

frequency ν and cyclotron frequency ω

ν / ω


Noise of discharge voltage
Noise of discharge voltage cathodes

Dependence of discharge noise of magnetic field


Discharge Noise Suppression by Admixture of Nitrogen cathodes

P.Allison, V. Smith,

et. al. LANL

no N2

QN2 = 0.46 sccm



Fast compact gas valve 0 1ms 0 8 khz

1 cathodes -current feedthrough;

2- housing; 3-clamping

screw; 4-coil; 5- magnet

core; 6-shield; 7-screw;

8-copper insert; 9-yoke;

10-rubber washer-

returning springs;

11-ferromagnetic plate-

armature; 12-viton stop;

13-viton seal; 14-sealing

ring; 15-aperture;

16-base; 17-nut.

Fast, compact gas valve, 0.1ms, 0.8 kHz




Discharge voltage cathodes

Noiseless operation

Discharge current

100 Hz

Extraction voltage

Tested for 300 hs of

continuous operation with H-

Current>100mA

Extraction current

H- current after

magnetic analyzer


Beam Formation and Diagnostics of SPS cathodes

with Penning Discharge


Emittance measurement direct brightness determination

Ion beam cathodes

Collector 1 with collimator for J.

Collector 2 with collimator s1 for B

Beamlet

Deflector Horizontal

Deflector Vertical

Screen with collimator s2 for B detection

Collector 3 for B detection.

B= I L2/s1 s2, s1=s2=0.1x0.1 mm2, L=250mm,

I~10-6 A.

Emittance measurement, Direct Brightness determination


Emittance diagramms
Emittance diagramms cathodes

0.5X10 mm mm

εxn 90% =0.06 π mm mrad

εyn 90% =0.2 π mm mrad

Tx~ 16 eV, Ty~2 eV

H- beam current 80 mA, Energy 23 keV,


Beam instability with a secondary electron emission
Beam instability with a secondary cathodeselectron emission


Beam instability with current density fluctuation
Beam cathodesinstability with current density fluctuation



Dependence of current and pick current density for different extraction voltages on discharge current


Binp version penning dt sps for umd
BINP version Penning DT SPS extraction voltages on discharge currentfor UMD

1- cathode;

2-anode;

3-extractor;

4- ground ext.;

5-magnet;

6-insularors;

7-cooler.

1 ms, 10 Hz, 1 A/cm2

Teff ~1 eV


Design of fermilab magnetron with a slit extraction
Design of Fermilab Magnetron extraction voltages on discharge current with a Slit Extraction


Fermilab Magnetron with a Slit Extraction extraction voltages on discharge current


Simulation of h ion beam extraction from the slit magnetron
Simulation of H extraction voltages on discharge current- Ion Beam Extraction from the Slit Magnetron

Current density

2

Electrodes trajectories and equipotentials

5

J, A/cm2

Y, mm

0

Y, mm

2

250

Emittance plot

0

0

5

10

X, mm

Slit 2x10 mm

I=87 mA

U=21 kV

neutral 95%

X’, mrad

-250

-2.5

X, mm

2.5


Discharge Parameters and Beam Intensity extraction voltages on discharge current

in Fermilab Magnetron

0

time, mks

200

0

Beam current, mA

80

0

time, mks

100


Beam Intensity vs Discharge Current and extraction voltages on discharge current

Extraction Voltage in Fermilab Magnetron


Extraction System of BNL Magnetron extraction voltages on discharge current


H extraction voltages on discharge current- Current vs Extraction Voltage

for Magnetron

H- Current, mA

Extraction voltage, kV


Design of the first Version of Semiplanotron extraction voltages on discharge current

SPS

V. Dudnikov, INP, 1976

1- Cathode 5cm long;

2- Anode -discharge chamber;

3- Magnetic insert;

4- Magnetic poles;

5-emission slit, d=0.5 mm;

6- Extractor;

7- cylindrical grove for plasma confinement;

8- plasma trap for discharge triggering.

H- Beam up to 0.9 A, 1 ms, 10 Hz, slit 0.7x45 mm2 ; 0.22 A, slit 1x10 mm2 .





Beam current vs an arc current for different slit geometry in the semiplanotron1
Beam Current vs an Arc Current for Different Slit Geometry in the Semiplanotron

Dependences of the Н- ion beam current on the discharge current have the N-shaped form with three sections: linear growth at small discharge currents, saturation or a falling section at medium currents, and linear, but slow growth at the high currents.


Polarized Negative Ion Source with a Resonance Ionizer in the Semiplanotron

A.Belov,V. Dudnikov, et. al.

analyzer

extractor

solenoid

Plasma Source

Ionizer, SPS

D-, D+,e, H-


DC SPS in the Semiplanotron

with a High Emission Current Density


Anode of dc sps
Anode of DC SPS in the Semiplanotron


Collector current Ic vs. discharge current Id and extraction voltage Vex

Extraction aperture of D=0.4 mm

Extraction aperture of D=1 mm


Compact DC SPS with Hollow Cathode Discharges extraction voltage Vex

1- cylindrical cathode body;

2- channel for cesium delivery;

3- channel for working gas;

4- insulator (ring);

5- anode chamber;

6- hollow cathode channel;

7- drifted plasma;

8- extraction aperture;

9- spherical emitter;

10- magnetic pole;

11- extractor;

12- ion beam.


Assembly of the negative ion source in vacuum chamber extraction voltage Vex

1- gas tube;

2- electric vacuum feedthroughs;

3- high voltage flange;

4- high voltage insulator;

5- high voltage feedthrough;

6- base flange;

7- cooling rods;

8- Cs catalyst supply;

9- cathode-emitter;

10- cathode insulator;

11- gas discharge chamber anode;

12- magnet poles;

13- suppression electrode;

14- extraction electrode;

15- permanent magnet;

16- high voltage insulators;

17- base plate-magnetic yoke;

18- ion beam;

19- vacuum chamber;

20- high voltage insulator.

.

Brookhaven Technology Group


Typical Assembling of CSPS on extraction voltage Vex

the Vacuum Flange


Emittance of dc sps 25 kev 1 5 ma
Emittance of DC SPS, 25 keV, 1.5 mA extraction voltage Vex


Duosps possible adaptation of nie in the real duoplasmatron
(DuoSPS) Possible adaptation of NIE extraction voltage Vex in the real Duoplasmatron


SPS with Helicon Plasma Generation and Ion/Atom Converter extraction voltage Vex

Ion flux conversion to fast atoms in converter.

Laser diagnostics and control cesium distribution. Cesium trapping by full ionization with laser excitation in discharge chamber.

Laser beam attenuation for control cesium density without discharge.


Helicon discharge plasma source for sps

A discharge in Hydrogen gas with helicon type antenna in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.

A quartz cylinder 34 mm ID, helicon antenna, solenoid and flanges are shown left. Ion current density of 0.1 A/ cm2 was extracted with a discharge power of 0.4 kW, RF frequency of 40 MHz. The same efficiency was produced before in RF ion source in the Budker Institute of Nuclear Physics (BINP), Novosibirsk, Russia in DC mode of operation with optimized resonance magnetic field.

Helicon discharge plasma source for SPS


Helicon Discharge Surface Plasma Source. in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.

1- gas valve; 2- discharge volume; 3- discharge vessel; 4- helicon saddle like antenna; 5- magnetic coil; 6- ion/atom converter; 7- electron flux; 8- emission aperture (slit); 9- extraction electrode; 10-suppression /steering electrode; 11- ion beam.


Antennas of RF plasma generator. in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.

With replacing of the ordinary helix antenna shown in (a) by saddle type (b) a plasma flux density was increased up to 5 times from 140 mA/cm2 to 700 mA/cm2 with 14 MHz RF frequency and power of 2.5 kW and magnetic field of B=86 Gauss. The plasma flux to the wall was reduced significantly. This big difference is determined by plasma generation near the wall with ordinary helix antenna and a much picked plasma generation with the saddle type antenna.

a- ordinary helix antenna; b- saddle type antenna.


Fnal sps in preaccelerator 0 75 mv 0 1 a
FNAL SPS in preaccelerator, 0.75 MV, 0.1 A in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.


Anl sps in preaccelerator 0 75 mev 80 ma
ANL SPS in preaccelerator, in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.0.75 MeV, 80 mA


LEBT with Solenoidal Focusing in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.

( BNL, LANL)


Semiplanatron sps on the flange
Semiplanatron SPS on the flange in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.

Schematic of semiplanotron SPS (cross section parallel to the magnetic field). 1-ion source flange; 2- insulator flange; 3-vacuum insulator; 4- gas discharge chamber-anode (st.st.) 5- cathode (molybdenum); 6- anode insert; 7-cathode insulator (ceramic); 8-discharge channel; 9- emission slit; 10- source holders; 11- high voltage insulators; 12- magnetic yoke; 13- base plate; 14- gas valve; 15- cathode nuts; 16 cesium oven; 17- ion beam; 18- extractor; 19- permanent magnets (NdBFe, 10x25x50 mm3); 20- magnetic inserts; 21- gas tube; 22-cathode cooling.


Semiplanatron sps on the flange1
Semiplanatron SPS on the Flange in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.

Schematic of semiplanotron SPS (cross section perpendicular to the magnetic field). 1-ion source flange; 2- insulator flange; 3-vacuum insulator; 4- gas discharge chamber-anode (st.st.) 5- cathode (molybdenum); 6- anode insert; 7-cathode insulator (ceramic); 8-discharge channel; 9- emission slit; 10- source holders; 11- high voltage insulators; 12- magnetic yoke; 13- base plate; 14- gas valve; 15- cathode nuts; 16 cesium oven; 17- ion beam; 18- extractor; 19- permanent magnets (NdBFe, 10x25x50 mm3); 20- magnetic inserts; 21- gas tube; 22-cathode cooling


Schematic of upgraded Compact Surface Plasma Source. in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.

Left-cross section along the magnetic field; right- cross section perpendicular to the magnetic field; 1-cooled anode; 2- high thermoconductive insulator AlN; 3- discharge gap; 4- cathode with channel for HCD; 5-plasma plate with emission aperture; 6- cooled high voltage flange; 7- first extractor-electron collector; 8- permanent magnet with magnetic poles and yoke; 9- high voltage insulators; 11- grounded extractor; 12- suppresser of positive ions; 13- ion beam; 14- gas valve; 15- cesium delivery system;16 -cooling chanel;17-magnetic yoke .


Dc csps with hc penning discharge yu belchenko binp
DC CSPS with HC Penning discharge in longitudinal magnetic field was developed and tested as plasma generator for H- source with Jim Alessi at the BNL in 1993.Yu. Belchenko, BINP

The source uses a Penning discharge with a hydrogen and cesium feed through the hollows in the cathodes. Discharge voltage is about 60–80 V, current 9 A, hydrogen pressure 4–5 Pa, magnetic field 0.05–0.1 T, and cesium seed ,1 mg/h. Negative ions are mainly produced on the cesiated anode surface due to secondary ion/atom emission. DC H- beam current up to 15 mA.


Sputtering yield

Sputtering and flakes formation are main reason of failures. Operation below a sputtering threshold is good for a lifetime increase.

Sputtering yield


Average current and source lifetime in hours and in A hr . Circle is anticipated parameters of BTG phase II.


Summary 1
Summary 1 Circle is anticipated parameters of BTG phase II.

The CSPS have high plasma density, high emission current density. They are very small, simple and effective have a high brightness in noiseless mode of operation, and high pulsed gas efficiency. The CSPS are very good for pulsed operation and continues operation during many months has been achieved. Negative ion formation, charge-exchange cooling of H- below 1 eV, high brightness beam extraction, formation, transportation, space charge neutralization, brightness preservation instability dumping are discussed. Practical aspects of SPS design, simulation and operation, a gas pulsing and cesium admixture control, lifetime enhancement of selected SPS are described and compared.


Summary 2
Summary 2 Circle is anticipated parameters of BTG phase II.

Features of all discussed CSPS are small volume, small gaps between electrodes, high plasma density and high emission current density. These features have complicated the long time operation of CSPS with high beam parameters, because a sputtering rate, flakes formation, deposition of insulators surface and probability of short circuit of electrodes should be high. But in many versions of CSPS was reached a very long operation time.


Summary 3
Summary 3 Circle is anticipated parameters of BTG phase II.

The operation time of ion source is limited by cathode erosion in plasma, deposition of conducting films to the insulators and flakes formation with a short circuit of a discharge gap between insulated electrodes. A typical current of DC discharge Id=1-10 A is small enough for long time conducting by these short circuit. It was observed, than during operation of CSPS with a pulsed discharge with low impedance forming line a flake formation is significantly suppressed and short circuit, created by deposition could be recovered. Short circuit created by conductive film deposition to the insulator or flakes can curry a low DC current but can be evaporated by high pulsed current. Evaporated material form a dust accumulated in any pockets in gas discharge chamber without disturbing of discharge.


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