Design and Performance Expectation of ALPHA accelerator

S.Y. Lee, IU2/26/2009

1. Introduction 2. Possible CIS re-build and parameters3. Issues in the Design of a small electron Synchrotron.4. Compact photon source5. Accelerator parameters and performance expectation

Problems of CRANE Linac in Radiation effect experiments:

–Parameter                                Requirement                            Goal –Dose Rate                                1E12 rads/sec                           5E12 rads/sec –Pulse width (narrow)                 10 - 50 nsec                             5 - 100 nsec –Pulse width (wide)                    ` 1 - 5 usec                                1 - 10 usec –Beam spot size (85% uniformity) 40 mm (diam)                        65 mm (diam) –Pulse rep rate                            10 shots/sec                            50 shots/sec –Energy                                                                                    40 - 60 MeV–No RF spikes in beam on target –Bremstrahlung Mode 2 – 3 cal/cm2

Our goal is to design a machine that can provide beam debunching, beam accumulation for radiation effect experiments and generate X-ray photons for future applications for both CRANE NSWC and IU Science Communities.

CIS: Circumference =17.364 m, Inj KE= 7 MeV, extraction: 240 MeV Dipole length = 2 m, 90 degree bend, edge angle = 12 deg.

ALPHA: No constraint on circumference (C=20m). Use CIS dipoles & cavity; Need Damping wigglers, chicane, electrostatic kickers & septum

Using a single quadrupole as in the DBA

Not a good idea!

1. Quadrupole does not work2. How about Robinson wiggler? – not effective in changing Jx

3. Gradient Damping wiggler

a. Maximize straight section so that there are space for future applicationsb. Make it easy to operatec. C=20 m, B1/B0=1.9 m-1. (AGS: B1/B0=4.1 m-1 )

Damping wiggler

Chicane for laser-electron interaction

cavity

Lambertsonseptum

Injection kickers

Pulse from linac

Extracted beam

Lambertson septum

Kicker 1 Kicker21. Beam in and out in one

revolution satisfies the CRANE requirement of steady state experiment.

2. The accelerator can accumulate 250 nC of charge in 10 or more turns and extracted in one turn for transient mode experiment (15J).

Debunch in 1 revolution

30 105

||

linac

Note that a large compaction factor is necessary for achieving de-bunching for the electron beams in a single path!

DBAε=7.8nmαc=0.15

Effect of the gradient damping wigglers2

0

4.0

W

W

P

P

Location of Bumpers

Dynamic Aperture

20

2

0

3

30

0

Emittance and damping time!

Vacuum

energy. offunction

a as emittance mequilibriu the

calculatecan we,2.9

25MeV,for 9.48 Choosing

)nTorr()/(

)/(

:emittance mequilibriu The

CO 40% H 60%

:ncompositio Vacuum

n compositio

vacuumon the depends :g

pressure. vacuum:P

emission.photon to

due excitation quantum :G

time.damping :

where,2

12

:equationevolution emittance The

dilution. emittance of source

another is scattering gas Beam

1

0

50

10

20

2

mg

Pg

gPGdt

d

g

Emittances are dominated by pressure in low energy,become natural emittances at high energy.

Touschek lifetime Toucheck lifetime is sensitive

to the parameter:

is the rf bucket height,

is the horizontal momentum spread

can range from 0.001 to 1.

we will need a lifetime of 1h or more.

It can also be varied by changing the momentum compaction factor

In summary, the ALPHA-project includes:

I: Put back CIS with 2 electrostatic kickers and one Lambertson magnet, install a surplus linac to demonstrate the single-turn injection and extraction scheme.

II: Refurbish and Install CIS cavity. Construct and install damping wigglers to verify the momentum compaction factor tuning and 10 or more turn accumulation! Commissioning the storage ring.

III: Build an injector LINAC for beam injection into the storage ring. In the future, one can Move CRANE Linac to IUCF for high intensity beam commissioning.

For eCIS design, the technology is well understood! The goal for the CRANE radiation effect experiments can easily be met!

For the Compact Photon Source, the technology of 100 MW laser is available!

IV: 90MHz cavity for photon source development, Design of Laser system, Optimization of Laser-beam interaction, photon flux and brilliance.

Accelerator Physics research with the ALPHA storage ring:

1.Quasi-isochronous accelerator beam dynamics (1st and 2nd order compaction factors)

2.Touschek Lifetime

3.Nonlinear beam dynamics

4.CSR

5.X-ray: Electron beams in an infinitely long linac (αc=0), encountering infinitely long weak undulators. What will be the electron beam distribution?