*************************************************************************
   71164
   The redshift distribution of the population of rich galaxy clusters
   depends sensitively on the cosmological density parameter, Omega_0. CDM
   numerical simulations show that the number density of rich, hot
   clusters at z~1 in an Omega_0=1 universe must be smaller by two orders
   of magnitude than that in an Omega_0=0.3 universe. Thus if a high
   temperature, high-z cluster is detected, we obtain a strong constraint
   on Omega_0; an Omega_0=1 universe can be rule out. We propose ASCA
   observations of high-z cluster 3C324 (z=1.206), which is thought to be
   rich and hot from the gravitational-lensing and ROSAT X-ray
   observations. With 100ksec observations, we can obtain a meaningful
   lower limit of the temperature which can constrain the density
   parameter.
 *************************************************************************