1. M. Preger LNF Accelerator Division Frascati Spring School 20/5/2005
Machine options
M. Preger
LNF Accelerator Division
Frascati Spring School 20/5/2005

2. 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

3. DAFNE layout 550 MeV e- DAMPINGRING LINAC 800 MeV e+ BTF KLOE FINUDA
X-ray / IR
(UV)

4. DAFNE DELIVERED L IN YEAR 2004-5 for KLOE
Up to 108 bunches
I-peak =1.92 A
I+peak = 1.35 A
Lpeak = 1.41e32cm-2s-1
Lday peak = 8.6 pb-1
Lmonth = 165 pb-1
L2004 > 850 pb-1

5. DAFNE short term schedule
2004
2005
2006
2007
KLOE
FINUDA
SIDDH-ARTA
SRFF (?)

6. The Strong RF Focusing experiment
The luminosity in a storage ring is inversely proportional to the vertical betatron function by* at the crossing point
L = luminosity
f = crossing frequency
N+/-= number of positrons/electrons per bunch
sx/y= r.m.s horizontal/vertical
beam size at crossing point
bx/y= betatron function at crossing point
g= relativistic factor
ro= classical electron radius
xx/y= beam-beam tune shift
eo= (ex+ ey) = beam emittance
K = (ey/ex) = coupling factor

7. The “hourglass” effectby
However, by* cannot be shorter than the bunch length, because of the “hourglass effect”
Bunch distribution

8. 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.

9. 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

10. 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 F and B factories
TESLA type
superconducting
cavity

11. 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

12. Photoinjector
Laser
Accelerating
sections
Undulator

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

15. DAFNE2
DAFNE2 is the upgrade of DAFNE from the present energy of 1.02 GeV c.m. up to the neutron-antineutron threshold, 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.

16. Injection
BTF
DAMPING RING
510 MeV
LINAC
e– 800 MeV
e+ 550 MeV
MAIN RINGS
1+1 GeV
TRANSFER
LINES X
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
We can inject directly on energy by adding new accelerating structures to the linac (synergic to the SparXino project)

17. 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

18. DAFNE2 DIPOLES The field must go from 1.2 T to 2.4 T at 1 GeV
The existing vacuum chamber imposes constraints on the dipole geometry
New dipoles should be 10% longer and all Sector magnets with bending radius from 1.40 m
to 1.54 m

20. Dipole Section – preliminary design

21. Magnetization curve

22. 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 F 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.

23. Both solutions are based on:
Design strategy
Both solutions are based on:
Shorter bunches and, consequently, lower by* at the crossing point
Stronger damping
Larger number of bunches
Larger colliding currents
Continuous injection

24. First solution
Minimize the down time after the end of the scheduled physics runs and operation restart (to be done in 2008)
Minimize recommissioning time
Minimize risks of failure
Minimize cost
Optimize just ONE-IR-AND-ONE-ENERGY solution.

25. 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

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

27. 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 T.
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

28. New collider inside DAFNE Hall
Long arc
With tunable R56 < 0
mini wiggler in dispersive zone for emittance tuning
and background minimisation insertion
Short arc
with highly tunable
R56 > 0 and R56 < 0
for alfac tuning
Space for
srff cavity
Long straight ( D=0 )
For injection, damping wigglers,
Tune knob

29. Short period superconducting wigglers
B = 4 T
E = 510 MeV
I2 = 10 m-1
Uo = 10 keV
7 poles + 2 half poles
15 poles + 2 half poles

30. IR design A B b*y mm 8 4 b*x m 0.7 0.5 Kq1 m-2 -19.4 -19.5 Kq2 m-2 8.2
b*y between 4 – 8 mm
b*x between 0.5 – 1 m
Crossing angle 20 mrad - tunable 20%
Sc quads A B
b*y mm 8 4
b*x m
0.7
0.5
Kq1 m-2
-19.4
-19.5
Kq2 m-2
8.2
8.4

31. Optimization of background
Last dipole
mx = 180°
Scraper
Beam direction

32. No SRFF, L=1÷2x1033cm-2s-1, 10÷20 fb-1/year
Emittance wiggler
Damping Wigglers
Emittance : 0.3 mm mrad
ac = 0.06
sL = 1 cm constant
Frf = 500 MHZ
V = 1 MV
t = 10 msec
I2 = 30 m-1
I3 = 60

33. With SRFF, L=3÷4x1033cm-2s-1, 30÷40 fb-1/year
Emittance : 0.35 mm mrad
ac = 0.017
sL max / sL min = 2.5
Frf1 = 500 MHZ
Frf2 = 1500 MHZ
V1 = 0.4 MV
V2 = 5 MV
t = 11 msec
I2 = 28 m-1
I3 = 56

34. Preliminary parameters
Energy (GeV)
0.5
Bdip – B wig (T)
C (m)
100
Uo (keV ) 29
L ( 1033 )
VRF (MV) 1
fRF (MHz)
500
V3RF (MV)
010 MV ex ac
SRFF
bx ( m )
sE/E
SRFF
by ( mm ) Qs
SRFF k
Prad (kW)
50 kW
Nbun
150
sL ( mm )
N±/bunch (1010 )
Ith
SRFF
Ibunch (mA) xx
Itot (A) xy

35. Injection
High luminosity
Short beam lifetime
Continuous injection

36. 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.

37. Injection at 510 MeV
high efficiency
new e- line
new e+ line

38. New t-charm factory
The Scientific Community of the Lab has also started to study the possibility of building a new t-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

40. Optical functions

41. Preliminary parameters
Energy
1.89 GeV B
1.8 T C
105 m Uo
328 keV L
1034 V1
2 MV
Frf
500 V3 ex ac
0.022
bx by
0.5 m 5 mm
sE/E k
0.003 P
900 kW
Nbun
160 sL
6 mm N+
IBOU
25 mA
xx xy
Itot
2.7 A

42. 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 t-charm project, due to their intrinsically longer beam lifetime
It would be hardly compatible with the high luminosity upgrade, which asks for continuous injection

43. LINAC low energy section modification
gun RF

44. LINAC high energy section modification
Etot ~ 2.1 GeV with 3 sections (11.4 GHz)
Etot ~ 1.8 GeV with 2 sections (11.4 GHz)
Etot ~ 1.5 GeV with 4 sections (3GHz)
Etot ~ 1.2 GeV
dogleg start

45. Radiation line layout
DAFNE
hall
Acc.
LINAC

46. Dogleg schematic layout
Dz  43 m y
Dy  3.38 m z

47. 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 t-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