Quantum field theory provides us with analytic predictions stating that the low-energy properties of any gapless 1D spin systems are universal, regardless of the underlying Hamiltonian. Due to recent progress in neutron instrumentation and the discovery of clean realizations of low-energy 1D Hamiltonians, we are now able to test these predictions in detail. We propose to study the universal temperature-scaling in the spin-ladder system DIMPY. Recent comprehensive studies (such as very fruitful experiments at LET) in combination with numerical DMRG calculations proved that this material is an almost perfect realization of a spin-ladder Hamiltonian. We propose to measure the low-energy spectrum (Ei < 1.5 meV) as a function of temperature (1.5K < T < 10K) in the field-induced Luttinger-Liquid regime with the LET spectrometer. We apply for 8 days of beam time. A cryomagnet is required.