ACCELERATORS

The UVX storage ring is a second-generation 1.37 GeV synchrotron light source. The injection system includes a 120 MeV linear accelerator and a 500 MeV booster synchrotron. The machine operates in decay mode and most of the beam lines are based on dipole magnets. Two RF stations are used to supply energy for the electron beam, each station including a single cell room temperature accelerating cavity and a 50 kW solid state amplifier operating at 476 MHz. The storage ring is housed in a temperature controlled tunnel and feedback systems are used to keep the beam orbit stable during the user shifts. Two diagnostics beam lines are used to monitor the beam.

OPERATION AND RELIABILITY

Over the last years, the UVX has been delivering around 3700 hours of synchrotron beam per year, with 24-hour operation from Mondays to Saturdays. The light source operates in decay mode and injections take place twice a day, with 30 minute scheduled time for each injection.

The machine usually operates in multi-bunch mode although single-bunch shifts can be provided on demand. In the multi-bunch mode, the initial current is 250 mA, decaying to about 130 mA at the end of the shift. The initial beam lifetime at small vertical coupling is typically of the order of 12 hours. In the single-bunch mode, the initial current is about 9 mA.

Injection in the booster takes place at 120 MeV and its top energy is 500 MeV. About 50 injection cycles are necessary to fill in the empty UVX storage ring with 250 mA. Injection takes place at low energy and the storage ring has to be ramped up to the operation energy after the accumulation process. At the end of the user shift the remaining current is ramped down to injection energy and a low energy top up process takes place.

The reliability of the light source, the ratio between the provided beamtime and the programed beamtime, has been usually close to 97,5% which is on the same level of the most competitive third generation light sources. In the last years the mean time between beam losses has been typically of the order of 60 hours.

MAGNETIC LATTICE

The UVX light source has a 6-fold symmetry DBA lattice.The magnetic lattice includes 12 1.67 T dipoles, 36 quadrupoles and 18 sextupoles. There are 6 straight sections of 2.95 m, 4 of them available for insertion devices, 3 of which are currently occupied with an EPU50 undulator, a 4T SCW60 superconducting wiggler and a 2T W80 hybrid wiggler. The machine is about 93 m long and the harmonic number is 148. A set of 18 horizontal and 24 vertical steering magnets is used by a 3 kHz fast orbit feedback system to keep the beam orbit within tolerances during the whole user beam shift.

The booster is a 2-fold symmetry racetrack synchrotron. The magnetic lattice includes 12 dipoles in two 180° FODO cell based achromatic arcs. The circumference of the booster is about one third that of the main ring and it operates at 0.2 Hz. The booster RF system includes a single cell cavity and a 2 kW solid state amplifier working at 476 MHz.

RADIATION SOURCES

Considering the two exits of each 1.67 T dipole, at 4° and 15°, the 6-fold symmetry of the lattice results in four types of radiation source according to the size and divergence of the synchrotron beam.

Source	Size (FWHM*) [mm]	Divergence (FWHM*) [mrad]
Dipole (any) at 15°	0.87 x 0.17	1.9 x 0.05
Dipole (even) at 4°	0.92 x 0.15	3.0 x 0.05
Dipole (odd) at 4°	1.10 x 0.20	0.9 x 0.05
Straight Section	3.86 x 0.04	0.2 x 0.06

LINHAS DE LUZ

In the UVX synchrotron, there are currently 20 beamlines installed, most of which are available to the user community (mostly from Brazil and Latin America).

14 beamlines are based on the 1.67 T bending magnets of the storage ring. Six of them are at the 15° exit of the dipoles (XAFS2, XRF, XPD, SAXS1, XAFS1, IMX), six of them are at the 4° exit of even dipoles (SAXS2, SXS, DXAS, SGM, XRD1, XRD2) and two of them are at the 4° exit of odd dipoles (IR, TGM).

Other three beamlines are based on insertion devices: one based on the EPU50 undulator (PGM), one based on the 2T W80 hybrid wiggler (MX2), and one based on the 4T SCW60 superconducting wiggler (XDS).

Finally, two diagnostics beamlines (DFE, DFX) are used to monitor the beam and one dipole beamline (IBL) is used for the development and testing of instrumentation both for UVX and for the new Synchrotron Light Source Sirius.

STORAGE RING PARAMETERS

Parameter	Value	Unit
Energy	1.37	GeV
Injection energy	500	MeV
Beam current	250	mA
Circumference	93.2	m
Average diameter	29.7	m
Magnetic lattice	DBA
Lattice symmetry	6
Dipole Bending radius	2.735	m
Dipole field	1.67	T
Number of dipoles	12
Free straight sections	4
Straight section length	2.95	m
Natural emittance (@max energy)	100	nm.rad
Horizontal Betatron tune	5.27
Vertical Betatron tune	4.17
Synchrotron frequency (@max energy, Vrf = 500 kV)	25	kHz
Natural horizontal chromaticity	-7.8
Natural vertical chromaticity	-9.5
Momentum compaction factor	0.0083
Energy dispersion	0.281	%
RF frequency	476.066	MHz
Harmonic number	148
Revolution period	311	ns
Horizontal damping time (@max energy)	7.8	ms
Vertical damping time (@max energy)	7.5	ms
Synchrotron damping time (@max energy)	3.7	ms
Beam lifetime (with/without coupling correction)	26/17	h
Energy loss per turn in the dipoles	114	eV
Radiated power at the dipoles (@100 mA)	11.4	kW
Critical energy in the dipoles	2.08	keV

BOOSTER PARAMETERS

Parameter	Value	Unit
Energy	500	MeV
Injection energy	120	MeV
Circumference	34	m
Larger axis	12.3	m
Shorter axis	7.9	m
Dipole bending radius	1.026	m
Dipole field	1.63	T
Number of dipoles	12
Natural emittance (@max energy)	284	nm.rad
Horizontal Betatron tune	2.27
Vertical Betatron tune	1.12
Natural horizontal chromaticity	-2.1
Natural vertical chromaticity	-2.5
Momentum compaction factor	0.129
RF frequency	476.066	MHz
Harmonic number	54
Revolution period	113.4	ns

UVX