Performance study of Pair Monitor. Kazutoshi Ito Tohoku university 23 rd Sep. 2008

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Norman Newman
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1 Performance study of Pair Monitor Kazutoshi Ito Tohoku university 23 rd Sep

2 Introduction Pair monitor measures the beam shape at IP, using pair background. The same charges with respect to the oncoming beam are scattered with large angle. The potential produced by the oncoming beam is a function of beam shape. The scattered particles carry the beam information. Pair monitor detects the scattered particles. Activity of Tohoku group. Development of the readout ASIC. Simulation study. e + beam e - e + IP e + e - e - beam Current status of simulation study is shown. 2

Simulation setup CM energy : 500GeV Beam size : (x( 0,y 0,z 0 )

3 Simulation setup CM energy : 500GeV Beam size : (x( 0,y 0,z 0 ) = (639nm, 5.7nm, 300m) Tools : CAIN (e+e- generator) Jupiter (Tracking emulator) Magnetic field : 3T with anti-did. Scattered e + distribution was studied. CH2Mask BCAL GLD beam pipe 400 cm IP Pair monitor e - e + e + e - Y[cm] distribution of e - hits Y[cm] distribution of e + hits Pair monitor Extraction pipe X[cm] X[cm] 3

4 Matrix method for beam size reconstruction The beam size is reconstructed by the Taylor expansion. m1 m2 mn matrix of the first order term = A x y + x, y B matrix of the second order term x y + Beam size (X) measurement variables (m) The beam size is reconstructed by the inverse matrix. x x y = [ A + x T B + ] -1 m The measurement variables are studied. 4

5 Variable 1 : Rmax R (sensitive to the horizontal beam size) Y[cm] X-Y distribution for the nominal : x = x 0 Y[cm] X-Y distribution for x = 1.5x 0 R R X[cm] X[cm] R distribution seems to depend on the horizontal beam size (x). The maximum R was investigated. 5

6 Variable 1 : Rmax Rmax Radius to contain 99.8% of all hits. R distribution for y=1y 0 1x 0 = 639nm 1.25x 0 = 799nm R max [cm] R max vs x Vertical size 1y 0 1.5y 0 2y 0 3y 0 1.5x 0 = 959nm R[cm] Horizontal beam size: x [nm] R max depends on the horizontal beam size( x ), dose not depend on the vertical size. 6

7 Variable 2 : Ratio (sensitive to x and y ) Y[cm] X vs Y R To derive the beam information, projection to -axis is checked. distribution (0.5xR max <R<0.8xR max ) X[cm] R- distribution for the nominal Vertical size y = y 0 y = 3y 0 R[cm] Projection to -axis [rad] [rad] There is the information of y in this region. 7

8 Variable 2 : Ratio The ratio defined NL/NN /NALL were obtained various beam size. R- distribution for the nominal Ratio = NL / N ALL (100bunches) R[cm] Ratio 1x 0 1.1x x 0 Region L [rad] 1.5x 0 Vertical beam size: y[nm] The ratio depends on the horizontal and vertical beam size( x, y ). 8

9 Variable 3 : Total number of hits (sensitive to x and y) The number of hits also have information of beam shape. Luminosity(L) L 1/ x y 1/N tot 1 / Ntot vs y 1.5x x 0 Number of hits(n tot 1.1x 0 /N tot 1/L x y 1x 0 Vertical beam size: y[nm] 1/N tot depends on both horizontal and vertical beam size. 9

10 Reconstruction of beam size max,, Ratio, 1/Ntot were set as the variable term (m, A and B). Rmax Rmax Ratio 1/Ntot measurement variables (m) = Rmax x (Ratio) x Rmax y (Ratio) y (1/Ntot) (1/Ntot) x matrix of the first order term A y x + x, y B y x x y matrix of the second order term x y = [ A + x T B ] -1 m Procedure of the beam size reconstruction. a)x0 = A -1 m b)x1 = [A+x0 T B] -1 m c)xn = [A+xn-1 T B] -1 m 10

11 Matrix component R max Ratio y[nm] y[nm] x[nm] x[nm] 1/N tot Matrix components are determined by fitting. y[nm] x[nm] 11

12 Results of the horizontal beam size reconstruction measurement of the horizontal beam size (x) x/x[%] Reconstructed with only the first order matrx. 5% x/x[%] Reconstructed with the second order matrix. 2% 100bunches Vertiacl size y = 5.7nm y = 8.55nm y = 11.4nm y = 17.1nm Vertiacl size y = 5.7nm y = 8.55nm y = 11.4nm y = 17.1nm Horizontal beam size: x true [nm] Horizontal beam size: x true [nm] Horizontal beam size can be measured with 2%. 12

13 Results of the vertical beam size reconstruction measurement of the vertical beam size (y) y/y[%] Reconstructed with only the first order matrx. 15% y/y[%] Reconstructed with the second order matrx. 3% 100bunches Horizontal size x = 639nm x = 702.9nm x = nm x = 958.5nm Vertical beam size: y true [nm] Vertical beam size can be measured with 3%. Horizontal size x = 639nm x = 702.9nm x = nm x = 958.5nm Vertical beam size: y true [nm] 13

14 Summary Pair monitor measures the beam shape at IP. Using pair backgrounds. The beam size (x, y) were reconstructed using the matrix of the Taylor expansion (second order). There are three measurement variables. R max sensitive to x. Ratio sensitive to x and y. 1/N tot sensitive to x and y. Horizontal beam size x resolution : 2% (~14nm). Vertical beam size y resolution : 3% (~0.2nm). m = A x + x T B x x = [ A + x T B ] -1 m 14

Using only HyCal. Graph. Graph

Using only HyCal. Graph. Graph Live charge weighted ep yield from all the 2GeV empty target runs Scattering angle from.7 to.9 deg, background dominated by upstream collimator (8%) Notice that here uncertainty from the live charge measurement