In spite of the wealth of measurements already performed, very little is known about the superconducting order parameter of quasi one dimensional organic compounds (TMTSF)2X. In this work, the effect of non magnetic impurities (ReO4) on the superconducting critical temperature (Tc) of (TMTSF)2ClO4 is investigated. Indeed, unlike conventional superconductors with isotropic gap, which keep the same sign all over the Fermi surface, are not sensitive to non magnetic impurities, we found that Tc is suppressed with a small amount of impurities. The decrease of Tc versus the impurity content (represented by residual resistivity) is well fitted by the Abrikosov-Gorkov formula.This result is in favor of a non conventional pairing and a gap which does not keep the same sign over the Fermi surface.A Spin Density Wave (SDW) phase appears when a larger amount of impurity is added. We found no coexistence between SC and SDW phases as in (TMTSF)2PF6 under pressure. We also measured the upper critical field along a, b' and c* axis versus temperature in order to compare it to the Pauli limit. This value corresponds to the maximum magnetic field that a conventional Cooper pair can tolerate. For (TMTSF)2X compounds this value is estimated to 2.16 T, we found a value superior to 3 T for fields parallel to a and b'axis. This result confirms also that the order parameter is non conventional. The magnetoresistance measurements for fields aligned along b' axis revealed an insulating behavior. An interpretation of this phenomena is that electrons are confined in a-b plane when a field is applied along b'axis.
