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The studies of SZ effects to date have largely been performed on relatively poorly-defined samples of clusters selected from ad-hoc lists, often using criteria which could lead to those clusters being unrepresentative of the total population, or even of clusters with identical masses, because of accidental effects of orientation, superposition, or transient dynamical state. Since the SZ effects are linear probes of cluster properties such as total energy content, they should provide excellent, well-defined, samples of clusters and SZ-selected samples would be ideal for such tasks as constructing the cluster-based Hubble diagram or examining the evolution of cluster gravitational potentials.

A major focus of current SZ effect work is therefore to plan for, and conduct, blind surveys of the sky to detect clusters solely through their SZ effects. The full range of observing techniques can be brought to bear on this task, but it is likely that radiometer and bolometer arrays on single dishes will provide the fastest means of performing surveys with arcminute angular resolution over many square degrees of sky.

To date, most SZ effect work has concentrated on simple cluster detection. However, with an increased number of detections, and the prospect of a sample of SZ-selected clusters, it will soon become important to follow up thse detections with higher angular-resolution observations (which are likely to be interferometer-based) to study the state of the gas within and around the selected clusters. Such observations might detect the kinematic effects from rapidly-infalling filaments, or see substructure from the accretion of filaments or subclusters. Further information can come from polarization observations of clusters showing the brightest SZ effects: measurements of both the radial and transverse velocities of those clusters would provide the dynamical information needed to make detailed tests of cluster formation models.

The requirements of these two programmes are somewhat different, and so distinct types of telescope are needed for surveys and detailed studies. Survey work is probably simplest using bolometer and radiometer arrays (e.g., BOLOCAM or OCRA) although tailored interferometers (e.g., AMI or AMiBA) can also be suitable. Detailed cluster studies will need interferometers or bolometer arrays like SCUBA-2 on large single dishes, since 10 arcsec or better angular resolution is needed. Two examples of specially-designed instruments are OCRA and AMiBA.

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