Development of gating foils using FPC production techniques Masaru Yoshikai (Fujikura Ltd.) Collaboration study by ILC-TPC Japanese Group 2018/5/29 , ALCW 2018@ Kyusyu University 自己紹介 xxxxx I'm happy to talk our activities on this conference. And Today I introduce our development results for ILC experiment.

Prodution of gating foils Contents Introduction Gating foil Positive ion feedback in ILC-TPC Prodution of gating foils Production method Development results (3) Summary - Gating foil for ILC-TPC (4) Our challenge First, I explain the contents of my talk. Today, I mainly explain the Gating foils for ILC-TPC, and I also introduce our FPC development actvity for High energy physics. About Gating foils. I explain What is the gating foil & Why we need to develop gating foils for ILC TPC And Next I explain our development results of Gating foils. And I explain the results and current situation. And Finally I expain a development of FPC for other experiment of HEP. 2/14

Introduction : Gating foil for ILC TPC ■ Time Projection Chamber for ILC TPC International Large Detector (ILD) is used as a particle detector of ILC. Time projection Chamber (TPC) with a micro pattern gas detector (MPGD) readout has been proposed as a central tracker. ILD TPC On this page I explain "Why we need the gating foil ?" Gating foils is special electrode foils for ILC TPC. TPC(Time projection chamber) using micro pattern gas detector readout has been proposed as a central tracker of the ILC detector. On this dectaor, We need to amplify the electorn to get signal on the readout of TPC. So Gas Electorn Multiplier (we call it "GEM") is planned to be used as a gas electron amplification device. GEM has many good points for the TPC, but has a problem of "Ion Feedback problem". Fig.1-1 Image of ILD Fig.1-2 Image of particle tracks Positive ions in TPC reduce point resolution. →"Ion feedback problem" "Gating Foil" is a device to solve the ion feedback problem!! 3/14

Gating foil ■ Gating foil for ILC TPC Operated in low voltage ＊GEM : Gas Electron Multiplier ★ Image of gating foil Cathode without gating foil with gating foil Gating foil E E GEM Readout PAD Fig 2. Image of Gating foil in TPC ★ Function of Gating foil Transmit electrons Stop the feedback of ions - Next I explain about the gating device. - We mount the foil structure gating device on the amplification module like this figure. - Gating foil have GEM-like structure like this figure. - We already know we can get high electron transmission when we operate the GEM in low voltage mode. - So we can close and open gate by reversing electric filed. Gate OPEN Gate CLOSE ★ Operation of gating foil Operated in low voltage Open and close by reversing voltage Fig 3. Electric field of gating foil 4/14

Requirement for gating foil Requirement for gating foil of ILC TPC Gating foil has GEM-like structure, but required specs are different. Rim width 70μm Fig 4-1. Picture of GEM Item Amplification GEM Gating foil Optical aperture ratio 22.7% ≧80% Hole size 70μm ≦ 300μm Hole pitch 140μm ≦335μm Rim width ≦35μm Insulator thickness 50μm or 100μm 12.5μm Foil size 170mm x 220mm I explain requirement for the gating foil. over 80% electron transmission is required to satisfy the performance of ILC-TPC. From the simulation results, the electron transmission is closely related to optical aperture of the gate. This table shows the details of the requirement, gating foil is required narrow rim and thin thickness insulator structure. Table 1. Requirement spec for gating foil and amplification GEM of ILC TPC 5/14

Production techniques of FPC and GEM ■Flexible Printed Circuit (FPC) - Fujikura is one of major FPC manufacturer in the world. FPC (Flexible Printed Circuit) ■Why does Fujikura develop Gating foil? GEM is producted by FPC production techniques. Difference of production is the mask design on photolithography process. Next I explain about the production of Gating foil First I explain why does fujikura try to develop the gating foil. Fujikura is one of major FPC maker in the world, and production techniques of amplification GEM are the same as FPC production. This table shows the production techniques using on GEM and FPC production. Single mask, Double mask use the photolithography and insulator removing, in case of FPC production this techniques are used in circuit formation. Key process GEM production FPC production Photolithography Hole design Circuit design Table 2. Production method of FPC and GEM We think we can apply FPC techniques to gaintg foil processing 6/14

Difficulty of gating foil processing (1) Very fine structure Item Gating foil Optical aperture ratio ≧80% Hole size ≦ 300μm Hole pitch ≦335μm Rim width (Hole pitch - Hole size) ≦35μm Insulator thickness 12.5μm Foil size 170mm x 220mm 35μm Fig5-1. Hole image of the gating foil Table 3. Required specs of gating foil (2) Size is very large Endplate of TPC prototype 100mm Next what is the difficulty of gating foil production. Gating foil have very fine structure, narrow rim and thin thickness Processing of the gating foil is so challenging even for FPC manufacturers. Fig5-2. Size of FPC and Gating foil Gating foil development is very challenging!! 7/14

Process of gating foil ■Process of gating foil We tested many process to make the gating foil. ■Process image (1) Laminate the photoresist film on copper Copper (Thick) Photoresist film Polyimide Copper (Thin) Important point (2) Form Honeycomb structure circuit on the thick copper side circuit width < 35um 今回いろいろトライしたけれど、最終的に製造したやり方を説明します。 Copper (Thick) Polyimide Copper (Thin) Honeycomb structure 8/14

Process of gating foil ■Process of Gating foil (3) Remove the polyimide by UV-YAG Laser Laser shot on all area Defocus beam of UV-YAG laser Using the circuit as Laser mask (4) Etch the copper from both side by etching liquid Etching speed is 2 times faster Etcher Gating foil structure 9/14

Circuit formation problem Development Results ■Defect of process 【Material problem】 【Process problem】 【Others】 Burr Circuit formation problem Creasing Contamination ■Completed process We already solved all problems. Optical aperture ratio 82.3% Thick copper side Thin copper side 10μm 304μm 12.5μm 31μm 2μm Fig6-1. Apperance of gating foil Fig6-2. Cross section of rim 10/14

Development Results (1) ILC-TPC module size (170 mm x 220 mm) The gating foil with large size is developped by using FPC techniques. Gating foil Fig7-1. Gating foil Fig7-2. Gating foil on module Fig7-3. Magnification of gating foil (2) Electron transmission ratio Electron transmission ratio over 80% is conformed by ILC-TPC Group. Gating foil please ask the test results to ILC-TPC Group. fig7-4. Gating foil on the Test module 11/14

Gating foil development is required to solve the ion feedback problem. Summary Gating foil development is required to solve the ion feedback problem. We tried to develop the gating foil by using FPC techniques. We faced many problems in the processing. We succeeded to make gating foil of ILC-TPC module size. 12/14

Our New challenge ■FPC for g-2/EDM experiment We make FPC for g-2/EDM experiment with collaboration of Kyushu University and KEK. 【Specs of FPC】 Min Line / Space = 35 um/35 um Circuit Q'ty : 2048 lines Longest line : L/S = 40 um/40 um & 200 mm (4) 　FPC Size : 100 mm x 270 mm (5) 　Structure : Combine 2 FPCs 210 mm conbine 2 FPCs 95 mm Fig8-1. Detector of g-2/EDM experiment Fig8-2. Characteristics of FPC for g-2 experiment 13/14

Fin. FPC technology ■Fine pitch ■Multi-layer ■Heat diffusing 　■Millimeter-wave 　■Noize sheild FPC technology 　■Component Assembly This is comercial. 　■High-Speed transmission 14/14

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Introduction : Positive Ion feedback in ILC TPC Positive-ion feedback from the gas-amplification region to the drift region can deteriorate the position resolution of TPC. Distortion Maximum 90um (Simulation results) Cathode Charged particle Positive Ion from GEM GEM GEM GEM amplification area(GEM) Readout PAD Position Ion is made from GEM Fig 2-1. Positive ion feedback in ILC TPC Fig 2-2. Image of ILC-TPC Required point resolution : better than 100 μm for long drift (~2m)