Blackbody energy detector, from Liboff's QM

Homework Statement

Problem 2.11 of Liboff's Introductory Quantum Mechanics, 1st edition

Suppose that you are inside a blackbody radiation cavity which is at temperature T. Your job is to measure the energy in the radiation field in the frequency interval $$10^{14}$$ to $$89 \times 10^{14}$$ Hz. You have a detector that will do the job. For best results, should the temperature of the detector T' be T' > T, T' = T, T' < T, or T' = 0; or is the temperature of the detector irrelevant to the measurement?

Homework Equations

There seems not lots of calculation.

The Attempt at a Solution

I've no idea how such a detector works. Dose it look like a blackbody itself which absorbs the radiation in the cavity?