Machine options

Machine options

M. PregerLNF Accelerator Division

Frascati Spring School 20/5/2005

Outline

• The present: facilities in operation and under construction

• The future: accelerators for subnuclear, nuclear and atomic physics

• The future: synchrotron radiation from Free Electron Lasers

DANE layout

LINAC 550 MeV e-

800 MeV e+BTF DAMPING

RING

FINUDA KLOE

X-ray / IR(UV)

DANE DELIVERED L

IN YEAR 2004-5

for KLOE

Up to 108 bunchesI-peak =1.92 A I+peak = 1.35 ALpeak = 1.41e32cm-

2s-1

Lday peak = 8.6 pb-1

Lmonth = 165 pb-1

L2004 > 850 pb-1

DANE short term schedule

2004 2005 2006 2007

KLOE

FINUDA

SIDDH-ARTA

SRFF (?)

The Strong RF Focusing experiment

• The luminosity in a storage ring is inversely proportional to the vertical betatron function y* at the crossing point

€

L = fN +N −

4πσ xσ y

€

ξx / y+ /− =

ro2πγ

N − /+β x / y

σ x / y σ x +σ y( )

€

L =πγ 2

r0fξ 2ε o

1+ k

β y

€

N =2πγ

roε oξ

L = luminosityf = crossing frequency

N+/-= number of positrons/electrons per bunch

x/y= r.m.s horizontal/verticalbeam size at crossing point

x/y= betatron function at crossing point

= relativistic factor

ro= classical electron radius

ξx/y= beam-beam tune shift

= (x+ y = beam emittance

(y/x coupling factor

The “hourglass” effect

0

0,02

0,04

0,06

0,08

0,1

-0,02 -0,01 0 0,01 0,02

s (m)

1 mm

5 mm

2 cm

y

Bunch distribution

However, y* cannot be

shorter than the bunch length, because of the

“hourglass effect”

The SRFF experiment• Short bunch length can be obtained by means of

a very large voltage in the RF system of the ring• On the other hand a short bunch in the whole ring

strongly contributes to the overall machine impedance, which is harmful to any kind of instabilities

• We therefore propose a novel scheme of a high voltage cavity associated with a strong dependence of the particle trajectory on its energy (momentum compaction), so that the bunch length changes along the ring, reaching its minimum value at the crossing point. The impedance generating elements in the chamber can be concentrated where the bunch is longer.

Drawbacks of SRFF• High RF voltage together with large momentum

compaction imply high synchrotron frequency, of the order of the revolution frequency

• The effect is strong coupling between betatron and synchrotron oscillations, introducing additional resonances which may lead to beam instability

• This can be avoided by adopting an alternative scheme, where the machine is divided into a section with positive dependence of trajectory length on beam energy and a negative one, resulting in a small overall momentum compaction. The required RF voltage in this case is also smaller, leading to a much lower synchrotron frequency

The SRFF experiment (cont)• This mode of operation has never

been tried elsewhere.The experiment can be realized in DAFNE, by building a new superconducting RF cavity at ≈10 MV, to be installed on one of the two crossing regions.Aims of the experiment are:

• Measure the bunch length at several positions along the ring to demonstrate its variations

• Check the single beam behavior as a function of the stored current to verify the possibility of realizing new kinds of synchrotron radiation sources, such as coherent emission in the terahertz region

• Check the behavior of the beams in interaction to test the potentiality of this mode of operation for new generation high luminosity and B factories

TESLA type superconducting

cavity

SPARC project (under construction)

• SPARC is a single pass Free Electron Laser test facility in the visible (green) wavelength range, now under construction at LNF as a joint venture between INFN, ENEA, CNR and Roma2, aimed at establishing know-how and technology for the realization of an X-ray FEL in the country

• It consists of a 150 MeV low emittance linear accelerator followed by a 12 m long undulator

• It is expected to start operation next year• Eperiments are already planned on SPARC, such as

laser-plasma acceleration and X-ray generation by Thomson scattering of laser radiation on the electron beam

LaserPhotoinjector

Acceleratingsections

Undulator

Future projects for subnuclear, nuclear and

atomic physics

• Modification of DAFNE to upgrade its c.m. energy from 1.02 Gev to ≈2.2 GeV

• Luminosity upgrade to reach >1033cm-2s-1

at 1.02 GEV without SRRF, option to go further with SRRF

• Realization of a -charm factory at >4 GeV c.m. with luminosity in the range of 1034cm-2s-1

DANE2

DAFNE2 is the upgrade of DAFNE from the present energy of 1.02 GeV c.m. up to the neutron-antineutron threshold, 2-2.5 GeV c.m., using as far as possible the existing systems and structures.

The luminosity required by the experiments for such a “light quark factory” is of the order of few 1032cm-2s-1, already achieved in DAFNE at its low energy of 1.02 GeV c.m.

Injection

1) DAFNE2 can use the existing injection system (linac and damping ring) at 0.51 GeV and reach 1–1.2 GeV per beam performing energy ramping in the main Rings

BTF

DAMPING RING510 MeV

LINAC

e– 800 MeVe+ 550 MeV

MAIN RINGS1+1 GeVTRANSFE

R

LINES

X

2) We can inject directly on energy by adding new accelerating structures to the linac (synergic to the SparXino project)

WHAT CAN BE USED FROM DAFNE

• DAFNE2 can exploit DAFNE hardware:– vacuum chamber– all quadrupoles and sextupoles– RF cavity– Feedback, vacuum system...

• But needs new:– stronger bending dipoles– 4 SC quads in IR2

DANE2 DIPOLES

The field must go from 1.2 T to 2.4 T at 1 GeVThe existing vacuum chamber imposes constraints on the dipole geometryNew dipoles should be 10% longer and all Sector magnets with bending radius from 1.40 m to 1.54 m

Dipole Section – preliminary design

1010 Steel

Permendur

Magnetization curve

0.71

1.06

2.42

2.09

1.94

2.25 2.292.34

1.72

0.5

1.0

1.5

2.0

2.5

3.0

0 50 100 150

H [kA* Turns]

B [T]

Bo

Bfe

Bperm

New accelerator initiatives @ 1.02 GeV c.m.

• The Accelerator Division at LNF is preparing a Conceptual Design Report for the construction of a collider at the energy of the resonance with a luminosity between one and two orders of magnitude larger than in DAFNE. We are considering two approaches:

• Keep the present layout, rebuilding part of the hardware. This solution should reach L≈1033cm-2s-1, the cost would be lower and the machine could be ready in a shorter time

• Build a new accelerator in the same building. The luminosity would be 2÷3 times larger than in the first solution, with accelerator physics background based on state-of the-art knowledge. The project can incorporate the possibility of adding a SRRF system, with the possibility of improving the luminosity further. Of course, cost and construction time would be larger.

Design strategy

• Both solutions are based on:

• Shorter bunches and, consequently, lower y* at the crossing point

• Stronger damping

• Larger number of bunches

• Larger colliding currents

• Continuous injection

First solution

Minimize the down time after the end of the scheduled physics runs and operation restart (to be done in 2008)Minimize recommissioning timeMinimize risks of failureMinimize cost

Optimize just ONE-IR-AND-ONE-ENERGY

solution.

Luminosity prospects

The luminosity projections are based on the extrapolation

of the estimated peak DAFNE performance: ≈1.5*1032cm-2s-

1 at 1.6A against 1.3A, ≈200pb-1/month, ≈ 1.8fb-1/year. That is a very close estimate of what Dafne can achieve in the 2005 KLOE run.

Current value is about 1.4*1032cm-2s-1 at 1.4Amps against 1.2Amps, 165pb-1/month 1.4fb-1/year.The upgrades are targeted at: - a factor > 5 luminosity increase at any given current, => with the present currents DAFNE33 should deliver:

L>0.65*1033cm-2s-1 , 0.8fb-1/month 7fb-1/year

- an increase in current up to 3 Amps/beam =>

L>1.5*1033cm-2s-1, 2fb-1/month, 18fb-1/year

Specific luminosity (L/I) improvement

The specific luminosity (Luminosity/Current) will be increased by a factor 5 by:

- reducing the the damping time by a factor >1.5- reducing the bunch lenght by a factor >4 (<8mm)

At the same time y at the IP will be reduced by a factor 4 and x will be decreased as well (probably necessary in order to have a more optimal beam aspect ratio).

Specific luminosity (L/I) improvement

The damping time can be reduced by a factor>1.5:

• by decreasing the gap of the DAFNE wigglers (from 37mm to <20mm), thus increasing the field from 1.7T up to 2.0-2.1T.

• by adding wigglers (2 pairs, same like the existing ones) in the second IR region

• superconducting wigglers could be adopted as well and installed at start-up or when ready, to reduce the damping time up to a factor 3

New collider inside DAFNE Hall

-30

-20

-10

0

10

20

-30 -20 -10 0 10 20

tutt

G

G

I

Long arcWith tunable R56 < 0mini wiggler in dispersive zone for emittance tuningand background minimisation insertion

Short arc with highly tunable R56 > 0 and R56 < 0for alfac tuning

Long straight ( D=0 )For injection, damping wigglers, Tune knob

Space forsrff cavity

Short period superconducting wigglers

7 poles + 2 half poles15 poles + 2 half poles

B = 4 TE = 510 MeVI2 = 10 m-1

Uo = 10 keV

IR design

y between 4 – 8 mm

x between 0.5 – 1 m

Crossing angle 20 mrad - tunable 20%

Sc quads

A B*y mm 8 4

*x m 0.7 0.5

Kq1 m-2 -19.4 -19.5

Kq2 m-2 8.2 8.4

Optimization of background

Last dipole

Beam direction

x = 180°

Scraper

No SRFF, L=1÷2x1033cm-2s-1, 10÷20 fb-1/year

Emittance : 0.3 mm mrad

c = 0.06

L = 1 cm constant

Frf = 500 MHZ

V = 1 MV

= 10 msec

I2 = 30 m-1

I3 = 60

Damping Wigglers

Emittance wiggler

With SRFF, L=3÷4x1033cm-2s-1, 30÷40 fb-1/year

Emittance : 0.35 mm mrad

c = 0.017

L max / sL min = 2.5

Frf1 = 500 MHZ

Frf2 = 1500 MHZ

V1 = 0.4 MV

V2 = 5 MV

= 11 msec

I2 = 28 m-1

I3 = 56

Energy (GeV) 0.5 Bdip – B wig (T) 1.7 - 4

C (m) 100 Uo (keV ) 29

L ( 1033 ) 1.95 4 VRF (MV) 1

fRF (MHz) 500 V3RF (MV) 010 MV

x 3. 10-7 c 0.07 SRFF

x ( m ) 0.7 0.5 E/E 6 10-4 SRFF

y ( mm ) 8 4 Qs 0.058 SRFF

0.007 0.007 Prad (kW) 50 kW

Nbun 150 L ( mm ) 11 5

N±/bunch (1010 ) 3.2 3.54 Ith

(mA)(@Z/n=0.5)14 SRFF

Ibunch (mA) 16 17.7

ξx 0.048 0.053 Itot (A)

2.4 2.65 ξy0.061 0.057

Preliminary parameters

Injection

High luminosity Short beam lifetime

Continuous injection

Layout of existing transfer lines:

Electrons and positrons use the same transfer line for injection into the Accumulator ring and (partially) from the Accumulator ring into the DAFNE rings. The common transfer lines magnets must change the current and some of them also the polarity during the switch from electron to positron mode.The switch takes at least 3 minutes.

new e- line

new e+ line

Injection at 510 MeVhigh efficiency

New -charm factory

• The Scientific Community of the Lab has also started to study the possibility of building a new -charm factory at 4÷5 GeV c.m. with luminosity in the 1034cm-2s-1 range

• Small amount of design work done by the Accelerator Division on this subject, mainly in the direction of estimating if the machine can be housed in the DAFNE hall

• First indications are positive but:• The machine circumference is ≈100 m, to be compared

with BEPCII which is 240 m long and is designed for 1033cm-2s-1

• BEPCII is scheduled to start operation end 2007 • Question mark on DAFNE building radiation safety

capability for a double ring high energy, high current collider

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-30

-20

-10

0

10

20

-30 -20 -10 0 10 20 30

Tau charm factory

I

IR

DA NE HALL

Optical functions

Preliminary parameters

Energy 1.89 GeV B 1.8 T

C 105 m Uo 328 keV

L 1034 V1 2 MV

Frf 500 V3 2 MV

x 1.5 10-7 c 0.022

x y 0.5 m 5 mm E/E 8.7 10-4

0.003 P 900 kW

Nbun 160 L 6 mm

N+ 3.5 1010 IBOU 25 mA

ξx ξy 0.03 0.05 Itot 2.7 A

SPARX-ino (small SPARX)

• The Institutes involved in SPARC (INFN-ENEA-CNR-RomaII) have been funded by the Italian Government to realize an R&D program to develop know-how and subsystem aimed at building in the near future a coherent X-ray source based on a single pass free electron laser

• There is a proposal to use these funds to upgrade the DAFNE Linac to higher energy in order to realize a source in the UV÷soft X-rays wavelength range

• This could be synergic to the high energy upgrade of DAFNE and with the -charm project, due to their intrinsically longer beam lifetime

• It would be hardly compatible with the high luminosity upgrade, which asks for continuous injection

LINAC low energy section modification

RFgun

LINAC high energy section modification

Etot ~ 1.5 GeV with 4 sections (3GHz)Etot ~ 1.8 GeV with 2 sections (11.4 GHz)Etot ~ 2.1 GeV with 3 sections (11.4 GHz)Etot ~ 1.2 GeV

dogleg start

Radiation line layout

DAFNEhall

LINACAcc.

y

z

Dy 3.38 m

Dz 43 m

Dogleg schematic layout

Summary

• The LNF Accelerator Division is running DAFNE for KLOE until the end of this year: FINUDA and SIDDHARTA will follow until the end of 2007.

• The SRRF experiment has been proposed and approved by the “New Accelerating Techniques” Committee of INFN: we are waiting for final decision and funding

• We are completing the construction of the SPARC Free Electron Laser, scheduled to start operation in fall 2006

• Studies for upgrading DAFNE to high energy and to high luminosity are under way

• The possibility to build a -charm factory inside the DAFNE hall or on a green field is being evaluated from the point of view of feasibility and cost

• The SPARX-ino proposal is already funded. Whether it will make use of the DAFNE Linac or not is still matter of discussion