In its normal mode of operation the Argonne Wakefield Accelerator Facilityuses a high charge (10-100 nC), short pulse (3-5 psec) drive bunch to excitehigh-gradient accelerating fields in various slow-wave structures. To generatethis bunch, we designed a 1.5 cell, L-band, rf photocathode gun with anemittance compensating solenoid to give optimal performance at high-charge; ithas recently completed commissioning. More recently, we have begun toinvestigate the possibility of using this gun in a high-brightness, low-chargeoperating mode, with charge equal to approximately 1 nC, for high-precisionmeasurements of wakefields. Two related measurements are reported on in thispaper: (1) measurements of the transverse beam envelope are compared topredictions from the beam dynamics code PARMELA; and (2) investigations intothe use of a modified 3-screen emittance measurement method that uses a beamenvelope model that includes both space-charge and emittance effects. Bothmeasurements were made for the 1 nC, 8 MeV beam in the drift region directlyfollowing the rf photocathode gun.
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