A flat-top beam generator comprising: a laser pulse repetition rate multiplier comprising: an optical cavity formed by two curved mirrors B01, B02), a first beam splitter,, a second beam splitter a first fold mirror and a second fold mirror, a beam compensator, a right-angled prism, said laser pulse repetition rate multiplier positioned to receive input laser pulses from a laser such that said input laser pulses are directed into said optical cavity along an optical path to the first beam splitter, wherein the first beam splitter is configured to split the input pulse into first and second portions, wherein the first portion is directed to the beam compensator which is configured to direct the first portion into the optical cavity to the second curved mirror which is configured to direct the first portion to the first curved mirror which is then configured to direct the first portion back to the second curved mirror which is then configured to direct the first portion back to the first curved mirror which is then configured to direct the first portion back to the first beam splitter, wherein the second portion is directed as a first output beam to the right-angled prism, wherein the right-angled prism is configured to divert the first output beam back to the cavity to the first fold mirror which is configured to direct the first output beam into the optical cavity to the first curved mirror which is then configured to direct the first output beam to the second curved mirror which is then configured to direct the first output beam to the second beam splitter, wherein the second beam splitter is configured to split the first output beam into third and fourth portions, wherein the third portion is directed into the optical cavity to the first curved mirror which is configured to direct the third portion to the second curved mirror which is configured to direct the third portion to the second fold mirror which is configured to direct the third portion back to the second beamsplitter, wherein the fourth portion is directed as a second output beam out of the optical cavity; wherein the second output beam exits the optical cavity as output laser pulses having an output pulse repetition rate that is four times that of the input laser pulses. a laser pulse repetition rate multiplier comprising: an optical cavity formed by two curved mirrors B01, B02), a first beam splitter,, a second beam splitter a first fold mirror and a second fold mirror, a beam compensator, a right-angled prism, an optical cavity formed by two curved mirrors B01, B02), a first beam splitter,, a second beam splitter a first fold mirror and a second fold mirror, a beam compensator, a right-angled prism, said laser pulse repetition rate multiplier positioned to receive input laser pulses from a laser such that said input laser pulses are directed into said optical cavity along an optical path to the first beam splitter, wherein the first beam splitter is configured to split the input pulse into first and second portions, wherein the first portion is directed to the beam compensator which is configured to direct the first portion into the optical cavity to the second curved mirror which is configured to direct the first portion to the first curved mirror which is then configured to direct the first portion back to the second curved mirror which is then configured to direct the first portion back to the first curved mirror which is then configured to direct the first portion back to the first beam splitter, wherein the second portion is directed as a first output beam to the right-angled prism, wherein the right-angled prism is configured to divert the first output beam back to the cavity to the first fold mirror which is configured to direct the first output beam into the optical cavity to the first curved mirror which is then configured to direct the first output beam to the second curved mirror which is then configured to direct the first output beam to the second beam splitter, wherein the second beam splitter is configured to split the first output beam into third and fourth portions, wherein the third portion is directed into the optical cavity to the first curved mirror which is configured to direct the third portion to the second curved mirror which is configured to direct the third portion to the second fold mirror which is configured to direct the third portion back to the second beamsplitter, wherein the fourth portion is directed as a second output beam out of the optical cavity; wherein the second output beam exits the optical cavity as output laser pulses having an output pulse repetition rate that is four times that of the input laser pulses.