GAS SECTOR PROJECTS FOR THE NSW MICROMEGAS: PERFORMANCE STUDIES AND QA/QC STATION DESIGN

Transcription

1 GAS SECTOR PROJECTS FOR THE NSW MICROMEGAS: PERFORMANCE STUDIES AND QA/QC STATION DESIGN T. Alexopoulos, E. Gazis, S. Maltezos, A. Antoniou, V. Gika, S. Karentzos, A. Koulouris, G. Koutelieris, E. Spyropoulou, P. Tzanis National Technical University of Athens (NTUA) M. Iodice 1, G. Sekhniaidze 2 1 Univ. of Roma III - Italy 2 CERN - Switzerland Thanks to our collaborator : Dr. B. N. J. Persson Jϋlich Germany 1

2 Outline Gas distribution system of NSW Micromegas Quadruplets Determination of the feasible gas sealing level Surface topography Gas tightness tests of Micromegas Quadruplets at CERN Development of a WinCC-OA based system for the Gas Tightness Station at BB5-CERN Conclusions 2

3 PROJECT 1 DESIGN OF THE GAS DISTRIBUTION SYSTEM 3

4 Gas system of NSW Micromegas 16 gas channels provide gas mixture to each NSW Each channel provide gas either to two LM wedges or to two SM wedges The gas inlet comes from the outer rim and the gas outlet goes to the inner rim. Trident manifolds Wedge manifold References ATL-COM-MUON Gas Distribution System 4

5 Wedge manifold test LEGRIS 1-TO-4 MANIFOLD MASS FLOW SENSORS INLET Testing setup at NTUA using four mass flow sensors References ATL-COM-MUON Gas manifolds design 5

6 Flow rate Q /( L/h) Obtained performance results DISTRIBUTION RESULTS WITH ARGON OUTLET No (%) 3-1 (%) 4-1 (%) 3-2 (%) 4-2 (%) 4-3 (%) Voffset (V) (Q=0) MEASURED Vo (V) Vo cor. (V) Q (L/h) MEASURED Vo (V) Vo cor. (V) Q (L/h) MEASURED Vo (V) Vo cor.(v) Q (L/h) MEASURED Vo (V) Vo cor. (V) Q (L/h) Manifold 1-to-4: Gas Distribution with Argon 16,00 14,00 12,00 10,00 8,00 6,00 4,00 2,00 0, Outlet No OPTIMAL CONFIGURATION Q (L/h) Q (L/h) Difference between the wedges: 3.9 % 6

7 Trident manifold test Gas flow distribution Z 1 Z 2 Z 3 Testing setup at NTUA using three mass flow sensors Design of internal impedances 7

8 PROJECT 2 DETERMINATION OF THE FEASIBLE GAS SEALING LEVEL SURFACE TOPOGRAPHY 8

9 Determination of the feasible gas sealing level The motivation was: I. To specify a benchmark acceptance limit of the Micromegas Quadruplets (MM QPs) during their production. II. To verify the performance of the surfaces and the rubber cord used in the MM-M0 construction and investigating the crucial parameters affecting the gas sealing performance III. To confirm the sensitivity of the Gas Leak Tightness Station being used in BB5. References ATL-COM-MUON Theoretical calculations ATL-COM-MUON Surface topography analysis 9

10 Contact Mechanics and Percolation theory Asperity contact region observed at magnification ζ It appears that complete contact occurs in the asperity contact region. The contact region at different magnifications Complete contact appears between the surfaces at the lowest magnification ζ = 1: A(1) = A 0. Increasing the magnification, it is observed that the solids are separated by an average distance u(ζ ). At the point where the non-contact area percolates, we have A(ζ c ) 0.4A 0 (white area). B. N. J. Persson and C Yang, J. Phys.: Condens. Matter 20 (2008) (11pp) 10

11 Surface topography analysis tools Definition of the 2D autocorrelation function: The Angular Power Spectrum (APS) expressed by via the 2D inverse FourierTransform: 2 Definition of roughness amplitude determined via the power spectrum in a finite wave vector radial region: where q q, q x y 2 (, ) ( ) i qr Rhh x y C q e d q iqr 2 C( q) R (, ) d 2 hh x y e r 2 r h q, q 2 qc( q)dq q q 0 For self-affine fractal surface: where H z h( x /, y / ) z h( x, y) 2 2 H 1 0 C( q) F( q) C q and H is the so-called Hurst exponent 11

12 Theoretical approach The equation describing the stress distribution P(σ,ζ) is a diffusion-like equation where the time is replaced by magnification and the position by the stress: P f 2 P 2 where f 2 G For the solution, two boundary conditions and one initial condition are used: and 0 P0 0 Initial condition (delta function of pressure at full contact P(,1) ( ) 0 Boundary conditions (zero pressure at the boundaries) P(0, ) 0 P(, ) 0 12

13 Solution for self-affine fractal surfaces First step: after some analytical work, we found the formula for the critical magnification: c 1 1 Cq E 50 (1 ) 1 2 2(1 H ) P0 H 2 1 2(1 H ) Second step: calculating the surface separation based on the rms roughness at the critical magnification. h H 2 H 1 h 1 h 1 ( P) 1 1 0, A 0, A 0, r c 2 2 H * h 2 0, Aq Hh 0 0, Aq0 E 2 E (1 H) P0 50 P0 (1 H) 1 H 2 H 1 13

14 Application: leak rate determination At a first glance: seems simple According to the Poiseuille Law for a Newtonian fluid and for a rectangular cross section of percolation channel of height u c and of width and length λ c (u c << λ c ). 3 Ly uc QL a ΔP L 12 L x x where, P 1.2 0R 1.2P PR 0R 0 1 * * E E E Looking deeply: it is very complicate A function of 1 variable and 8 parameters L L Q P u u h H q f and a 1 Surfaces roughness amplitude Roll-off wave number * y E ΔP 3 y 1 ΔP L( 0) c c ( 0, A,, 0, ( )) 14.4R P R f ( ) Squeezing pressure Rubber s radius Hurst exponent P0 1 Squeezing ratio 2 * Gas viscosity Apparent contact separation E 3 at critical magnification f ( ) 1 1 Plane elastic modulus Pressure difference Rubber contact length 14

15 General analysis procedure 0.3 4P0R 1.2P0R Lx 2a * * E E 15

16 D f Angular Power Spectrum of FR4 H=3 -D f Slope: -2(H+1) Fractal dimension D f q o The Angular Power Spectrum (APS) obtained by AFM for FR4 in an area region of 100 μm x 100 μm using 512 samples. The fractal dimension is determined four methods. The scaling of the spatial frequency axis has to be converted to wave vector modulus. 16

17 Parameterization model Cq ( ) Hh 2 0, A 0 2 2q0 2 2H 0, A q0 2 Hh C( q) 2 q q Cq ( ) Cq q 1 q 0 2 H n H1/ n a) By the theory (red curve) assuming self-affine fractal surface b) by using a proposed (modified) K-correlation model for fitting better the region around the roll-off wave number (blue curve). The roll-off wave number is located at the intersection point of the asymptotes defined by the model. 17

18 Theoretical result of feasible leak rate of MM LM2 QP dp/dt=0.07 mbar/h P o =0.32 MPa (3.2 bar) (squeezing ratio ε=0.26) 18

19 Summary of the results for the LM2 Described in the next section 19

20 PROJECT 3 GAS LEAK TIGHTNESS TESTS OF MICROMEGAS QUADRUPLETS AT CERN 20

21 Gas leak test of the LM2-M0 QP: the PDR method used Obtained leak rate by laminar model converted to 3 mbar (12/2016) Q L (L/h) (dp/dt) t=0 mbar/h 0.025± ±0.05 Results of LM2 Doublet at 3 mbar (9/2016) Q L (L/h) (dp/dt) t=0 mbar/h ± ±0.01 Improvement factor Gas gap spacer=5.18 mm D of o-ring, from 6.4 to 7 mm P o, from 2.1 to 3.2 bar Experimentally obtained: 4.0 Theoretically predicted:

22 Gas leak test of MM SW: the FRL method at work MM SW LEAK RATE MEASUREMENTS AT CLEAN ROOM OF LAB 154 The differential signals were recorded by 10 readings of 100 averaging per reading References ATL-COM-MUON Upgrade using LIA (stage-2) ATL-COM-MUON Implementation & calibration ATL-COM-MUON Investigation & proposal 22

23 3D model of the FRL setup 6 ½ digits Differential signal reading (signal ~ 75 mv, tare ~40 mv, net signal ~ 35 mv) V o =DD.DXXX mv with running aver. of 100 values (X are the fluctuating digits) 5 V IN: layer 1+layer (2,3) OUT: layer (2,3)+layer 4 IN: layer 1 OUT: layer 4 23

24 Summary of the gas tightness test of MM SW GAS LEAK RESULTS OF MM SW (gauge pressure=3 mbar, volume V=7.17 L, effective length Ly=0.22xL y,lm2 =9.5 m) Rubber 6 mm, ε=0.133 EPDM shore A 20 Method used: PDR Rubber 7 mm, ε=0.257 EPDM shore A 20 Method used: FRL Q L experimental (stˑl/h) Q L theoretical** (stˑl/h) (dp/dt) t=0 exper. (mbar/h) (dp/dt) t=0 theor. (mbar/h) Exper. leak factor (ref. to 0.6 mbar/h) 0.267± ± ± ±0.2 62± ±0.003* ± ± ± ±0.9 Improvement factor 5.5±0.4 7±3 * Overall error * * The values concern the feasible sealing limit. Nevertheless, a noticeable improvement has been accomplished, the gas tightness of the MM SW is still below its own nominal acceptance limit. 24

25 PROJECT 4 DEVELOPMENT OF A WINCC-OA BASED DATA SYSTEM FOR THE GAS TIGHTNESS CONTROL STATION AT BB5-CERN 25

26 WinCC-OA (PVSS) The Supervisory Control And Data Acquisition (SCADA) system chosen by CERN Main Criteria: Scalability Large Distributed System Openness Programming Language (C) API (Managers&Drivers) Multiplatform (Windows, Linux) ATLAS Detector Control System 26

27 Gas Tightness Station to be used at BB5 - CERN A data acquisition, monitoring and processing software based on WinCC-OA has been developed dedicated for the Flow Rate Loss (FRL) and Pressure Decay Rate (PDR) methods Supports: Monitor and Trending of mass flow, pressure and temperature sensors Alarm Handling for the leak rate of MM MPs Archive/Export of data 27

28 How Gas Tightness Station works? Stage 1: Baseline FRL/PDR Setup Voltage output of mass flow, pressure and temperature sensors Stage 2: FieldPoint NI Analog to Digital Converter 16-bit Stage 5: GTS settings panel MM type and channel settings Stage 4: GTS selection panel Selection of method (FRL/PDR) Stage 3:WinCC-OA Stage 6: GTS main control panel Monitoring and data acquisition Stage 7: Archive/Export of data Last Stage: Data analysis 28

29 Overall test of GTS with emulated leak Obtained data by using the FRL method for the needle 32G-CN9 (D int =108 μm) with argon flow at around 2 L/h The separation distance represents the leak rate 29

30 Conclusions The overall gas distribution system and also the two main manifolds ( Wedge and Trident ) have been designed, optimized and are going to be used as baseline solutions. Our theoretical calculations have shown that the feasible gas sealing of MM QP can be about 7 times below the nominal acceptance limit. Crucial gas tightness tests of Micromegas LM2 Module-0 and MM SW we have done at CERN this year. The specific-new method, FRL, we introduced and proposed for the GTS has been successfully implemented and is going to be used also in the constructions sites. A system based on the WinCC-OA has been fully developed to be applied in the gas tightness station at BB5-CERN. 30