# Presentation: 544733

## High Brightness Negative Ion Sources with High Emission Current Density

- Vadim Dudnikov
- Fermi National Accelerator Laboratory

*SNS, Oak Ridge *
*March 6, 2002*

## Contents

-   Introduction.
-    Historical remarks.
-    Change-Exchange injection.
-    Negative ion production in surface- plasma interaction.
-     Cesium catalysis.
-    Surface Plasma sources- SPS.
-    Discharge stability noiseless operation.
-     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.

## History of  Surface Plasma Sources Development

**History of  Surface Plasma Sources Development**

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

## General diagram of the surface-plasma mechanism

**General diagram of the surface-plasma mechanism**
** ****for production of ions in a gas discharge**

## SCHEMATIC DIAGRAM OF THE BASIC

**SCHEMATIC DIAGRAM OF THE BASIC**
** ****VERSIONS OF SPS**

***(a)***** planotron (magnetron) flat catode**
***(b)***** planotron geometrical focusing (cylindrical      and spherical)**
***(c)***** Penning discharge SPS (Dudnikov type SPS)**
***(d)***** semiplanotron**
***(e*****) hollow catode 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

## Emittance, brightness, ion temperature 

- Emittance

- Normalized emittance

- Normalized brightness

- Half spreads of energy of the
- transverse motion of ions

- Reduced to the plasma emission slit

- Characteristics of quality of the beam formation:

**Emittance, brightness, ion temperature**

- l

- δ

- Δα

- Δx

- y

- x

## H- detachment by collisions with various particles

**H****- ****detachment by collisions with various particles**
**and resonance charge-exchange cooling**

- Resonance charge -exchange cooling

## Discharge stability and noise

**Discharge stability and noise**

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

- The effective transverse electron
-  mobility μ  vs effective scattering
-  frequency ν and Larmor frequency ω

- B, kG

- n,1016 cm-3

- noisy

- noiseless

- n*

- Bmin

- no discharge

- μ

- ν / ω

- noiseless

## Discharge noise suppression by admixture of nitrogen

**no N****2**

**Q****N****2**** = 0.46 sccm**

**Discharge noise suppression by admixture of nitrogen**

## H- Beam Intensity of SPS

**H****-**** Beam Intensity of SPS**

- Beam intensity vs discharge current
- for first version of semiplanatron

- Evolution of H- beam intensity in ISIS

- Years

## Simulation of H- ion beam extraction from the slit magnetron 

**Simulation of H****-**** ion beam extraction from the slit magnetron**

- Electrodes trajectories and equipotentials

- Slit 2x10 mm
- I=87 mA
- U=21 kV
- neutral 95%

- 0

- 10

- 5

- 0

- 5

- X, mm

- Y, mm

- 0

- 2

- 2

- Current density

- Emittance  plot

- -2.5

- 2.5

- -250

- 250

- X, mm

- X’, mrad

- J, A/cm2

## Computer Simulation of H- Beam FormationPBGUNS

- 0           4             8             12           16           20          24            28

- 12

- 6

- Z, mm

- R, mm

- Electrodes, trajectories and equipotentials

- Aperture diameter 0.4 mm,  I=1.5 mA

- Emittance plot

- R, mm

-   -50                         0                         50

- 25

- 0

- -25

- R’ ,mrad

- 0

## Beam Formation and Diagnostics of SPS

**Beam Formation and Diagnostics of SPS**
**with Penning Discharge**

## 100 Hz

- Discharge voltage

- Discharge current

- Extraction voltage

- Extraction current

- H-  current after
- magnetic analizer

- Noiseless operation

- Tested for 300 hs of
- continuous operation

## Fermilab Magnetron with a Slit Extraction

**Fermilab Magnetron with a Slit Extraction**

## Discharge Parameters and Beam Intensity 

**Discharge Parameters and Beam Intensity **
**in Fermilab Magnetron**

- 200

- 100

- 80

- 0

- 0

- time, mks

- Beam current, mA

- time, mks

- 0

## Beam Intensity vs Discharge Current and 

**Beam Intensity vs Discharge Current and **
**Extraction Voltage in Fermilab Magnetron**

## Extraction System of BNL Magnetron

**Extraction System of BNL Magnetron**

## H-  Current vs Extraction Voltage

**H****-****  Current vs Extraction Voltage**
**  ****for Magnetron**

- H- Current, mA

- Extraction voltage, kV

## Semiplanotron SPS with a Slit Extraction

**Semiplanotron SPS with a Slit Extraction**

## Beam Current vs an Arc Current for Different Slit Geometries in the Semiplanotron

**Beam Current vs an Arc Current for Different Slit Geometries in the Semiplanotron**

## DC SPS

**DC SPS**
** ****with a High Emission Current Density**

## Typical Assembling of CSPS on

**Typical Assembling of CSPS on**
** ****the  Vacuum Flange**

## LEBT with Solenoidal Focusing

**LEBT with Solenoidal Focusing**
** ****( BNL, LANL)**

## Emittance Plots after Magnetic LBT  

**Emittance Plots after Magnetic LBT **

## Semiplanotron SPS with Slit Extraction for High Intense NI Beam Production

**Semiplanotron SPS with Slit Extraction for High Intense NI Beam Production**

## Summary

**Summary**

## Slide 28