Low energy operation of the DIAMOND light source

Abstract Within the last decade storage ring free-electron lasers (SRFELs) have reached UV output wavelengths and beyond: several facilities have achieved down to 250nm and quite recently below 200nm. The design of DIAMOND, the third-generation replacement for the existing SRS light source at Daresbury Laboratory, has been optimised at 3 GeV to provide high quality output for the scientific community, mainly from a range of insertion devices. In this paper we propose an additional DIAMOND regime at 1-1.5 GeV in an attempt also to include an SRFEL which would be of major benefit to users needing high quality, high brightness UV/VUV radiation. Such variable ring operating energy will have significant implications, not least in achieving acceptable beam lifetimes. In addition, enhanced beam coherent instabilities (notably microwave) at low energy will affect the single bunch length (peak current) and energy spread which will in turn limit the achievable FEL gain. All these factors will have to be assessed in the detailed design stages of DIAMOND. DIAMOND LIGHT SOURCE The recent successful demonstration of an SRFEL on the ELETTRA light source [1], together with earlier experience at LURE (Super-ACO) and elsewhere, has encouraged interest in the incorporation of such advanced facilities in all leading light sources. The normal operating mode of DIAMOND at 3GeV is described in detail elsewhere FEL OPERATING MODE When operating in optimised FEL mode, the storage ring will be populated with bunches spaced apart in time by twice the round trip time in the FEL cavity, ensuring energy transfer occurs as frequently as possible; the cavity length is always chosen to be a sub-harmonic of the storage ring circumference, whilst satisfying other, practical constraints. The final circumference of the DIAMOND storage ring has not yet been fixed but may be finalised at 528 m (an increase on the present 489 m layout [2] to budget for additional elements), giving a harmonic number of 880 at 500 MHz RF frequency. With 8 equally spaced bunches this leads to a required cavity length of 33 m, which is reasonable (cf. the ELETTRA device which has a cavity length of 32.4 m [1]). Since a very small vertical emittance is not necessary for FEL operation, a conservative coupling value of 3% has been assumed for these calculations, which should both be readily achievable and provide a satisfactory Touschek lifetime; both greater coupling and larger emittance could be selected if necessary. The momentum acceptance will be the primary limit on the beam lifetime at low energies, via Touschek scattering and quantum lifetime; the 4% dynamic and physical acceptance limit specified for 3 GeV operation BUNCH MODELLING To provide peak currents of tens of Amperes, as will be needed for useful FEL gains, bunch currents of several milliamperes are required. At these currents the effects of bunch lengthening from potential well distortion (PWD) and from the microwave instability (MI) are large, but are beneficial in that they provide low enough number densities within the bunches to give an acceptable Touschek lifetime; however the issue is whether sufficient peak current can then be maintained, together with acceptable energy spread. The ZAP code [3] was used to predict the effect on bunch parameters of PWD and MI (details are given in [4]); however, the implementation of Brück's approximatio

Seeded gas thrusters and related system components

A program involved with the construction and test of a number of laser heated thrusters is described. These thrusters, with a cavity approximately 23 cm long and 3.5 cm in i.d., are to be tested by NASA at a later date with a laser beam focused through the throat to heat hydrogen propellant containing an opacifier. The heated propellant exhausts through a supersonic nozzle with a 0.6 cm throat at 3000 C. Thrust stands and control systems were furnished with the thrusters. The report describes radio frequency plasma heated hot and cold flow simulation tests by the contractor

1976 Growing season results report

1. 76BU15 - Sunflower varieties x rates of seeding x times of seeding on Busselton Sand at Ruabon. 2. 76BU4 - Miscellaneous species x rates of H.23408 Treeton. 3. 76AL6 - Rape varieties under severe blackleg conditions. 4. CB49 - Seed softening methods and effort of harrowing on emergence. 76MA9 - Miscellaneous Crop Trial. CB49 Trials 76BA27 - Effect of Harrowing on germination. Fluctuating temperatures. Fate of Other Trials: 76AL35, 76AL37), 76AL38), 76AL39), 76DE4, 76JE28

Rapeseed. 3. Varieties and their growth patterns in Western Australia

RAPE belongs to the genus Brassica which also includes such plants as the garden cabbage, wild turnip and cultivated mustard. The name is derived from the Latin word rapum . meaning turnip

Growing sunflowers in south-western Australia

The oil produced from sunflowers falls into the polyunsaturated group and usually commands a premium price on world markets. Some Western Australian farmers seeking to diversify their cropping programmes in the face of marketing difficulties for many agricultural products are trying sunflowers, although commercial production has not yet been achieved. This article sets out some basic information for farmers wishing to try sunflowers

Rapeseed production in Western Australia

RAPESEED production began in Western Australia in 1968 when a few acres were grown. In 1969, about 20 growers ptanted small acreages for about 80 tons of seed. In 1970, up to 20,000 acres will be grown, and a total of 40,000 acres seems possible within the next few years

Subterranean clover establishment in the wheatbelt

Care and attention to detail will greatly increase the chances of establishing good subterranean clover pastures in the wheatbelt. PASTURE ESTABLISHMENT usually takes second place to cropping in the wheatbelt, with many farmers bunging in a bit of clover and hoping for the best. The worst often transpires, with either patchy stands or complete failure resulting. Using cheap methods of establishment is a short-sighted approach and a waste of energy and resources

Fertility build up under northern wheatbelt pastures

Experiments on two farmers\u27 properties demonstrated that legume pastures increase the fertility of northern wheatbelt soils. Crops on legume pastures had higher yields than crops on volunteer pasture. The experiments also indicated the most productive legume species for each situation and demonstrated that nitrogen added by legumes has a residual effect in the soil