M. Biagini, INFN-LNF

For the Tau/charm Study Group

XCIX Congresso SIF, Trieste 25 /09/13

Overview A t/charm Factory, an e+e- collider with very high luminosity at

the 2-4.5 GeV center of mass energy, to be built on the Rome University at Tor Vergata campus, was studied by the Consorzio N. Cabibbo Laboratory and the INFN Frascati Laboratories

This project is the natural evolution of the flagship Italian project SuperB Factory, funded by the Italian Government in 2010 with a budget that turned out to be insufficient to cover the total costs of the project, and then cancelled in Dec. 2012

The study of rare events at the t/charm energy was already planned as a Phase-II of SuperB. This design keeps all the unique features of SuperB, including the polarization of the electron beam, with the possibility to take data in a larger energy range, with reduced accelerator dimensions and construction and operation costs

Accelerator study group LNF team CabibboLab team M. Biagini M. Boscolo A. Chiarucci A. Clozza A. Drago S. Guiducci C. Ligi G. Mazzitelli R. Ricci C. Sanelli M. Serio S. Tomassini

S. Bini

F. Cioeta

D. Cittadino

M. D’Agostino

M. Del Franco

A. Delle Piane

E. Di Pasquale

G. Frascadore

S. Gazzana

R. Gargana

S. Incremona

A. Michelotti

L. Sabbatini

LNS team

ESRF & Pisa team

G. Schillaci

M. Sedita

P. Raimondi

S. Liuzzo

E. Paoloni

t/charm Factory main features Energy tunable in the range Ecm = 1-4.8 GeV

1035 cm-2 s-1 peak luminosity at the t/charm threshold and upper

Symmetric beam energies

Longitudinal polarization in the electron beam (60-70%)

Possibility of e-e- collisions (to be studied)

Beam parameters for reasonable lifetimes and beam currents

Low power consumption lower running costs

Injection system scaled from the SuperB one

Possible applications: SASE-FEL @2.4 6 GeV

Beam Test Facility line

Beam parameters Beam parameters to reach a baseline luminosity of 1035

cm-2 s-1 @ 2 GeV/beam have been chosen

An upgrade to 2x1035 cm-2 s-1 can be possible by increasing

the beam current

Design features are the same as for the SuperB design: “Large Piwinski angle & crab waist sextupoles” collision

scheme

Low H-emittance lattice

Small H-V coupling ultra low V-emittance

Small IP b functions and beam sizes

Beam-beam tune shifts < 0.1

Same RF frequency as PEP-II (re-use of cavities)

Low beam power

Table of parameters @ 2 GeV/beam

Baseline design L=1035, with possibility to increase currents for 2x1035 cm-2 s-1

Intra Beam Scattering and hourglass factors included

Beam power about 15 times less than the SuperB baseline one (4 MW (HER) and 2MW (LER) of RF power)

Luminosity vs Energy

At low energy (last column) insertion of 8 wigglers is foreseen to keep same damping times Polarization will be maximum around 4 GeV c.m

Tau-Charm Layout @ Tor Vergata

t-charm complex view

LINAC

Damping Ring

Storage Rings (preliminary)

IP

TLs

Main Rings lattice: Arc

Y Sexts mux=3pi muy=pi

X Sexts mux=3pi muy=pi

X Octupoles

The sextupoles arrangement allows for a very good correction of non-linearities and provides a very large dynamic aperture without the Final Focus

Main Rings lattice: Final Focus

X Sexts mux=muy=pi Y Off Phase Sexts

X Off Phase Sexts

Crab Sext

Y Sexts mux=muy=pi

The Final Focus sextupoles need to compensate for the huge chromaticity coming from the final doublets. Their effect on the dynamic aperture is important but has been minimized as much as possible

Final Chosen tolerated Values

S.M.Liuzzo, ESRF, Università Tor Vergata 15

Lifetimes and backgrounds Backgrounds and lifetime are two issues strictly

connected one to the other, even if they have different implications for the accelerator design and operation, being determined by the same physical process that may induce particle losses

Backgrounds can be cured with detectors shielding, masking and collimator systems, while a short lifetime can be handled with continuous top-up injections

A Monte Carlo simulation is used to determine the beam lifetimes and the beam-stay-clear needed for acceptable beam loss rates

Beam lifetimes estimate

Final Focus collimation system

20

Final Focus collimation system (similarly to SuperB)

20

COL1 COL2 COL3

SFX0

COL4

SFX4

PRIMARY SECONDARY

Collimators are located where bx and Dx are large

M. Boscolo, Tau-Charm at High Luminosity, May 29th 2013

H-collimators

SDY0 SDY4

V-collimators

Main Rings magnets

Dipole

Gradient dipole

Quadrupole

Sextupole

!CHAOS Control System

CUs are the drivers attached to devices

DOC is the RAM

KVDB is the HardDisk

UI,EU are the CPUs running user applications

Chaos can be view as a distributed computer

BSON is the BUS

!CHAOS (Control System based on Highly Abstracted Operating Structure) is the proposed software infrastructure to realize the Control System

Damping Ring mechanical layout

Damping Ring

Main Rings

Main Rings side by side

The present maximum separation between main rings is about 3.5m 3.5m

Feedbacks

Primary Network

Secondary Network

t-charm alignment case study

Only the outer reference points of the secondary network are visible.

Tau-Charm Injection System The preliminary layout of the injection system is based on

the design of the SuperB injection system

The same design for the linac and damping ring lattice is used

The main difference with respect to the SuperB design is the fact that only positrons are stored in the Damping Ring (DR)

As for the SuperB case, the linac can be used to accelerate electron pulses for an FEL synchrotron light source

Tau-Charm Injection System

0.6 GeV 1.0 GeV 1.3 GeV

Bypass

Positron Positron

Source DR

e-

e+ FEL Line

e+

e-

To MRs

FEL photoinjecto

r

Linac L1 Linac L3 Linac L2 e-

Bunch

Bunch

Compressor

Total electron linac energy 2.9 GeV Total positron linac energy 2.3 GeV

Linac L1 Linac L2 Linac L3

N. of klystrons 3 6 7

N. of cavities 9 18 21

Max. Energy (GeV) 0.62 1.24 1.45

The number of klystrons and cavities allows to reach the maximum The number of klystrons and cavities allows to reach the maximum positron energy of 2.3 GeV also with one klystron off

Positron Damping Ring • The preliminary magnetic layout of the damping ring is

completed

• The mechanical design of magnets and supports is in progress

• The mechanical layout is ready for next step: vacuum, diagnostic, radio frequency, survey and alignment

DR magnets design

Dipoles

Sextupoles

Long And short Quadrupoles

Tau/charm as a SASE-FEL

Conventional Facilities

133

The beam for the SASE FEL would be produced by a dedicated high brightness photo-injector

similar to that used at SPARC-LAB at LNF. A 50 Hz pulsed magnet will be used to combine the FEL

beam with the Tau/Charm injection beams. The maximum linac energy for the electron beam is

2.9 GeV, a long space is available for the FEL extension: Linac extension, transfer lines,

undulators and experimental halls.

The FEL injection system (S-band, 2.856 GHz) is composed by one 1.6 cell RF photo-injector

followed by 2 TW structures embedded in a solenoid magnetic field as required to operate in the

Velocity Bunching mode. It is a copy of the SPARC-LAB photo-injector, 8 m long.

The linac can be operated for the FEL in single or multi-bunch mode with a pulse length lower

than 800 ns, to be compatible with SLED system, and with a repetition rate of 50 Hz. The charge

per bunch can be chosen to better match the emittance and peak current requirements for the

FEL operation.

After the photo-injector the beam is accelerated up to 2.9 GeV in Linac L1, L2 and L3. Two pulsed

magnets are needed to separate the FEL bunches from the Tau/Charm bunches in the region of

the positron converter and other two can be used in the region of Damping Ring injection and

extraction, between linac L2 and L3. In this regions two magnetic bunch compressor systems can

be installed, suitably designed to increase the peak current.

A layout of the Tau/Charm complex with the FEL facility is shown in Figure 7.1.

Figure 7.1 - Tau/Charm complex with the SASE-FEL option.

To estimate the photons wavelength we consider an electron beam that traverses an

undulator, emitting electromagnetic radiation at the resonant wavelength:

r= u2 2

1=au2( ) (7.1)

1. Linac tunnel

2. Modulator and klystron

building

3. Damping Ring

4. Main Rings

5. Collider hall

6. Assembly hall

7. Vacuum Lab

8. Cryo Lab

9. Magnetic measurement

10. HVAC building

11. Electric station

12. Electric substation

13. Linac banda C tunnel

14. Undulators unnel

15. Experimental hall

• Possibility to drive a SASE X-ray FEL using the 2.4 GeV Tau/Charm Linac • To achieve an energy of 6 GeV (1.5 and 3 Angstrom photon wavelength)

additional Linac sections can be installed at the end of the last Linac, using the C-band (f = 5712 MHz) technology, which is being developed at LNF in the framework of the EU-TIARA project, and will be soon mounted at SPARC-LAB

• Assuming an accelerating gradient of 40 MV/m, additional 80 m of Linac sections (about 40) should be added (total Linac length 300 m)

Accelerator Report

Distributed mid-July, INFN-LNF publication September

Accelerator Report ToC 1. Introduction

2. Collider Main Rings

- Luminosity and Beam parameters

- Main Rings lattice

- Interaction Region design

- Dynamic Aperture and tolerance to errors

- Backgrounds and lifetimes

- Intra Beam Scattering

- E-cloud instability

3. Injection Complex

- General layout

- Positron Source

- Damping Ring

- Linac specifications

- Transfer Lines

- Injection into the Main Rings

4. Accelerator Systems – Diagnostics – Feedbacks – Controls – Vacuum Sysstem – Radio Frequency – Magnets (DR, MR) – Mechanical engineering – Survey and alignment – Power electronics

5. Conventional Facilities - Site - Mechanical layout - Infrastructures and civil engineering - Fluids - Cryogenics - Electrical engineering - Health Safety and Environment

6. Costs and schedule 7. Tau/charm as a SASE-FEL facility 8. Tau/charm as a beam Test

Facility

Conclusions A new infrastructure for a low energy Flavour Factory, with

possible applications in other fields such as FEL and BTF has been designed

A Report on the accelerator design (150 pp.) has been published and can be the base for a fast TDR phase

The N. Cabibbo Laboratory is in place to construct and run such a facility

The estimated cost of the facility would be entirely covered by the promised “SuperB” funding

However a decision on the future of the Flagship projects has not been taken yet, and the PNR (Piano Nazionale Ricerca) for the next 3 years is still in progress

INFN will have to take a final decision before the end of this year