# Presentation: 737771

## 111

- Antimatter

## Congratulations and Thanks Ron!

-   Plasma Fusion Center, MIT

-   Physics of Plasmas

-   ‘95 Plasma Study

## New Tools for Antimatter Studies Positron Plasmas and Trap-Based Beams*

**Cliff Surko**

- James Danielson
- Toby Weber
- Tom O’Neil
- Mike Anderson

- * Supported by NSF,
- DOE/NSF Partnership

## Antimatter in our world of Matter

**Plasma Physics********enabling the study  **
**and use low-energy antimatter**

## The real reason we are making antihydrogen...

- But the real reason we’re making antimatter ...

## Why Trap and Cool Antimatter? 

- Isolate interactions with matter
- Atomic/molecular physics
****Laboratory astrophysics
- Density dependent processes
****Pulsed, bright beams
-        		(e.g., plasma diagnostics, materials analysis)
****Antihydrogen production
****Electron-positron plasmas
****BEC positronium

**e****+**

## A Near-Perfect “Antimatter Bottle” The Penning-Malmberg Trap

-     Angular Momentum
-     No torques  *L**z** = *            is constant   No expansion!

- (Malmberg & deGrassie ‘75; O’Neil ‘80)

- John
- Malmberg

*E* x *B* plasma
- rotation
*f*E = c*n*e/*B*

## Buffer-Gas Positron Trap

-  Trap using a N2-CF4 			gas mixture
-  Positrons cool to 300K 			(25meV) in ~ 0.1s

- Surko PRL ‘88; Murphy, PR ‘92

- _30%_
- _trapping efficiency_

## Buffer-gas Accumulator

**Buffer-gas Accumulator**

- Positron plasma

- Gas in

- Positrons
- in
- (flux ~ 1 pA)

- Cryopumps

- 1.8 m

## Trapping Antimatter

- Goals
- Long-term storage
- High capacity
- Cold, dense plasmas
- Portable antimatter traps
- Considerations
- Space charge:  10 kV  ~ 1011 e+/cm* 	Confinement at high plasma densities?
- Cooling  cool ~ 0.2 s @ 5 tesla

- *  cylindrical plasma

## Overview of Positron Trapping

- Improve vacuum

- Improve B-field

- Computerized optimization

- Improved trap

- Stacking
- ATHENA

- Solid neon moderator

- Year

- trapped positrons

##   Increase positron storage capacity

-   Plasma compression for lifetime and
- 	density control
-   Extraction of finely focused beams

- New Tools for Antimatter Physics

## Multicell Trap for Large Ntot*

- RF Electrodes

- DC Electrode

- 2Rp

- Lp

- L

- Side View

- Positron Plasma

- Multicell Trap for Large Ntot*
- Many “beaded rods” in parallel

-  _Design Parameters_

-  B = 5T
-  n ~ 3x1010 cm-3
-  Lp ~ 5 cm
-  Rp ~ 0.14 cm
-  T ~ 2 eV
-  Ntot ~ 1010 (1 cell)
-  c ~ 1 kV

- Total number of cells ~ 100
-  Ntot ~ 1012

- *Surko and Greaves, *Radiation Physics and Chemistry* (2003)

- B

## Multicell Positron Trap Electrodes

- master cell

- 2 banks of 19 storage cells

- Danielson, Phys. Plasmas (2006)

## D/Rw ≥ 0.8

- Danielson, Phys. Plasmas (2006)

- D/Rw ≥ 0.8

- fD = fDo[1 - (D/Rw)2]-1

## “Rotating-Wall” Compression of Positron Plasmas

- Compress radially using a rotating electric field.
- Good coupling over broad range of frequencies.

- Applications:
- 	- ‘infinite’ confinement times
- 	-  increase plasma density
- 	-  create bright antiparticle beams

- (Huang, et al., Anderegg, et al.,
- 	Hollmann, et al., ‘95 - ‘00)

## Transition/bifurcation

- _________________________________________________

- Danielson PRL (05); Phys. Pl. (06)

- electron
- plasma

## Slide 18

## Zero-Frequency-Mode (ZFM) Drag is Key to the Dynamics

- Dependence on fRW

- Danielson, O’Neil, Surko,  PRL, submitted

## RW Compression in the Strong Drive Regime

-   Good physical model of transitions,
-     upper and lower fixed points.
-   Now explore limits, high densities
-    and low temperatures for applications

## Brightness Enhancement Using Traps

-  Rotating wall compressed plasma
-  Slow release creates beam narrower than plasma
-  RW and inward transport fill “hole” created by positron release

- Danielson, APL (2007)

## Beam Extraction

- Small-beam limit:

- Plasma

- electron plasma

- (10 s pulses)

## Slide 23

## What’s Next 

- Some Near-term Goals

-   Explore the density limits of RW compression
-   Create a 1 meV positron beam
-   Develop a multicell trap

**Long-term challenge:  a portable antimatter trap**

##       For references see:

-       For references see:
- 	http://positrons.ucsd.edu/