Target assembly comprising insulating target, field and collector meshes

Claim 1

A PICKUP TUBE COMPRISING AN ENVELOPE AND HAVING THEREIN AN ELECTRON BEAM SOURCE FOR FORMING AND DIRECTING A BEAM OF ELECTRONS ALONG AN AXIAL PATH, A PHOTOCATHODE SENSITIVE TO AN INPUT RADIATION POSITIONED AT THE OPPOSITE END OF SAID ENVELOPE WITH RESPECT TO SAID ELECTRON BEAM SOURCE, ANNULAR ELECTRODE MEMBERS POSITIONED BETWEEN SAID PHOTOCATHODE AND SAID ELECTRON SOURCE, A TARGET ELECTRODE ASSEMBLY OF SMALLER DIAMETER THAN SAID ANNULAR ELECTRODE MEMBERS POSITIONED BETWEEN SAID PHOTOCATHODE AND SAID ELECTRON SOURCE INCLUDING AN INSULATING TARGET, A COLLECTOR ELECTRODE POSITIONED ON THE SIDE OF SAID TARGET FACING SAID PHOTOCATHODE AND A FIELD TERMINATING ELECTRODE POSITIONED ON THE SIDE OF SAID TARGET FACING SAID ELECTRON SOURCE, SAID TARGET INCLUDING AN INSULATING FILM AND AN ANNULAR SUPPORT RING, SAID COLLECTOR ELECTRODE INCLUDING A MESH AND AN ANNULAR SUPPORT RING, AN ANNULAR CLAMPING MEANS FOR RETAINING SAID TARGET AND SAID COLLECTOR ELECTRODE AND SECURING SAID TARGET AND SAID COLLECTOR ELECTRODE TO AN INNER PORTION OF ONE OF SAID ANNULAR ELECTRODES, SAID FIELD TERMINATING ELECTRODE INCLUDING A MESH AND AN ANNULAR SUPPORT RING AND MEANS FOR MOUNTING SAID FIELD TERMINATING ELECTRODE TO SAID CLAMPING MEANS.