Beam emittance reduction during operation of Indus-2.

Indus-2 storage ring is a 2.5 GeV third generation synchrotron radiation source. This source was commissioned using a moderate optics. Beam injection was accomplished using an off momentum electron beam to avoid difficulties faced in storage of beam at 550 MeV. The injection procedure and relevant beam dynamical studies are discussed. The switch over from the moderate optics to low emittance optics is done at 2.5 GeV after storing the electron beam. The procedure evolved to reduce the beam emittance and its implementation during the operation is discussed.

An analytical study of double bend achromat lattice.

In a double bend achromat, Chasman-Green (CG) lattice represents the basic structure for low emittance synchrotron radiation sources. In the basic structure of CG lattice single focussing quadrupole (QF) magnet is used to form an achromat. In this paper, this CG lattice is discussed and an analytical relation is presented, showing the limitation of basic CG lattice to provide the theoretical minimum beam emittance in achromatic condition. To satisfy theoretical minimum beam emittance parameters, achromat having two, three, and four quadrupole structures is presented. In this structure, different arrangements of QF and defocusing quadruple (QD) are used. An analytical approach assuming quadrupoles as thin lenses has been followed for studying these structures. A study of Indus-2 lattice in which QF-QD-QF configuration in the achromat part has been adopted is also presented.

Studies of beam injection with a compensated bump and uncompensated bump in a synchrotron.

Synchrotron radiation sources Indus-1 and Indus-2 have a synchrotron as the common injector. A three kicker compensated bump injection scheme was employed for beam injection into this synchrotron. The stored beam current in the synchrotron is higher, when all the three kickers are operated at the same current than when kickers are operated at currents required to generate compensated bump. Beam dynamics studies have been done to understand why this happens. Theoretical studies indicate that higher stored current in the later case is attributed to smaller residual oscillations of injected beam. These studies also reveal that if the angle of the injected beam during beam injection is kept varying, the performance could be further improved. This is experimentally confirmed by injecting the beam on rising part of the injection septum magnet current pulse.

Design and characterization of combined function multipole magnet for accelerators.

This paper presents the design and analysis of a multipurpose combined function magnet for use in accelerators. This magnet consists of three corrector magnets: (i) skew quadrupole, (ii) horizontal dipole, and (iii) vertical dipole magnets, along with the main sextupole magnet. The strength of the corrector magnets is smaller than that of the main sextupole magnet. The strength of all the four magnets can be varied independently. The excitation strength required to produce skew quadrupole gradient and the presence of various multipole components in the magnet are estimated using first order perturbation theory. The experimental data for the variation of the sextupole strength and its higher order multipoles in the presence of skew quadrupole excitations are presented and compared to the theoretical predictions. Simulation using two-dimensional fine element code, Poisson, is also done. Results obtained from all the above three methods are found to be in good agreement with each other. The variations of skew quadrupole gradient for different sextupole excitations are also measured. The validity of this theory is also checked for various combinations of excitations including the case where magnet gets saturated. The excitation strengths required for producing the horizontal and vertical dipole fields are estimated analytically along with the presence of various multipoles. Theoretical predictions of permissible multipoles are compared to the results obtained from simulation.

Empowerment and advocacy: reflections on action research with Bangladeshi and Pakistani families who have children with severe disabilities.

The concepts of empowerment and advocacy, and how they impinge on power relationships for service providers working with black and Asian communities, are explored through the findings of a 20-month project carried out between 2000 and 2001 with 19 Pakistani and Bangladeshi families who have children with severe disabilities in Birmingham. This action research project evaluated an advocacy project designed to improve the quality of life for Pakistani and Bangladeshi families with at least one child with severe disabilities. The objectives included improving access to resources, services, information and support in ways which were non-stigmatising, and which were sensitive to the particular needs of the children and their carers. The present paper discusses four main themes: (1) advocacy and empowerment in practice; (2) issues of the efficacy of advocacy and of consultation within advocacy; (3) individual empowerment versus the families' needs; and (4) cultural and gender issues which emerged from the analysis of the study. The authors identify features of empowerment which must be addressed in advocacy services which are sensitive to ethnic differences. These issues must be addressed if services are to reap their potential to make a positive impact on the lives of the most vulnerable and powerless members of the community.

Attitudes towards disability amongst Pakistani and Bangladeshi parents of disabled children in the UK: considerations for service providers and the disability movement.

It has sometimes been assumed that religiously based explanations for and attitudes to having a disabled child have led to the low uptake of health and social services by ethnic minority families in the UK. A series of semi-structured interviews were held between 1999 and 2001 with 19 Pakistani and Bangladeshi families with a disabled child as part of an evaluation of an advocacy service. The families' understandings of the causes of their child's impairment, whether they felt shame and experienced stigma, and whether these factors influenced service uptake and their expectations of their child's future are reported. While religious beliefs did inform the ways in which some families conceptualised their experience, the families' attitudes were complex and varied. There was little evidence that religious beliefs and associated attitudes rather than institutional racism had resulted in the low levels of service provision which the families experienced prior to the advocacy service. There was also no evidence that the families' attitudes had been informed by the disability movement. The implications for service providers and the movement are considered.