Shin, B.K. Chung, M. Hahn, G. Sung, C.K. JACoW Publishing Geneva, Switzerland 2673-5350 978-3-95450-236-3 10.18429/JACoW-IBIC2023-WE3C02 English 318-320 emittance simulation experiment electron background Contribution to a conference proceedings 2023 2023-12 https://doi.org/10.18429/JACoW-IBIC2023-WE3C02 https://jacow.org/ibic2023/papers/we3c02.pdf We have developed a highly precise 4D emittance meter for X-Y coupled beams with 4D phase-space (x-x’, y-y’, x-y’, y-x’) which utilizes an L-shaped slit and employs novel analysis techniques. Our approach involves two types of slit-screen image processing to generate pepper-pot-like images with great accuracy. One which we call the "differential slit" method, was developed by our group. This approach involves combining two slit-screen images, one at position x and the other at position x + the size of the slit, to create a differential slit image. The other method we use is the "virtual pepper-pot (VPP)" method, which combines x-slit and y-slit images to produce a hole (x,y) image. By combining that hole images, we are able to take extra x-y’ and y-x’ phase-space. The "differential slit" method is crucial for accurately measuring emittance. Through simulations with 0.1 mm slit width using Geant4, the emittance uncertainties for a 5 nm rad and 0.2 mm size electron beam were 5% and 250% with and without the "differential slit", respectively. In this presentation, we provide a description of the methodology, the design of slit, and the results of the 4D emittance measurements.