Non-BPS branes in a type-I orbifold

We analyse the spectrum of non-BPS branes in the type-I theory on the orbif old T-4/I-4. We present a detailed analysis of the action of the worldsheet parity Omega on the different D-brane boundary state sectors of type IIB o n T-4/I-4, using the covariant formulation. Using these results we derive t he spectrum of branes in the type-I orbifold. We find Z(2)- and Z- charged non-BPS branes. A study of the stability of these branes in the type-I orbi fold is also presented. We find that the type-I non-BPS D-particle and D-in stanton remain stable in the orbifold. The D-particle carries no charge whe reas the non-BPS D-instanton can carry twisted R-R charge.