Status of New TPC( Ⅱ ) Performance Study Yohei Nakatsugawa LEPS Meeting in Taiwan

What we have done TEST Ⅰ experiment in October 2005  Pad Response Function TEST Ⅱ experiment in December 2005  Position Resolution in X-Y plane In all tests, only MWPC part was used.

Pad Response Function estimated avalanche position(mm) central pad position(mm) estimated avalanche position(mm) sigma= 6.99×10 -2 mm mean = 0 Usually, Gaussian is used. simulation (intrinsic) I searched for better function … avalanche position = 0 (fixed)

Pad Response Function F(x)= 1 (p 1 +p 2 (x-p 3 ) 2 ) a a=3.5 sigma = 4.431×10 -2 mm mean = 6.62×10 -3 mm p 3 = avalanche position Is this really better function? Pseudo Lorentzian better than Gaussian

TEST Ⅰ (October 2005) 55 Fe pulse motor anode wire trigger To decide PRF, We measured the dependence of pad gain on hit position. Source spot is on layer4. TPC was set vertically and moved by 500μm step by pulse motor. (total: -2500~2500μm  one pad width) X-ray source ( 55 Fe, 5.9keV) was used. collimator One anode wire above the layer4 was used as trigger. layer4 32mm 3mm16mm x y z y pad plane 1mm

TEST Ⅰ set up This is actually not a photo of TEST Ⅰ set up, but it was like this.

Analysis Source event selection Three pads in the source spot are hit. Other layers are not hit. PRF measured (x) =∫ ｄｘ ’ PRF(x’)*exp[ -{ x - x’ } 2 /(2*σ 2 ) ] σ=1.106 (by Monte Carlo ） Unfolding the dispersion of X-ray assuming Gaussian Compare Gaussian and Pseudo Lorentzian

Analysis measured Pseudo Lorentzian Gaussian χ2 Gaussian 10.5 Pseudo Lorentzian 5.2 Pseudo Lorentzian is better.

TEST Ⅱ ( December 2005 ) γ Pd converter magnet e-e- e+e+ up veto scintilator start upstart down scintilator solenoid trigger condition: up start up start down To see angle dependence of XY resolution, data were taken at 0°(figure),±12.5°,±25° TPC angle. rotation Sector 1 & 4 could not be read out due to geometry in the hatch. (Cable length was not enough.) ~25cm (~5cm width) dipole Layer9 was also read out.(  new FADC)

TEST Ⅱ set up TPC side view e-

TEST Ⅱ set up TPC side view e-

TEST Ⅱ set up TPC front view

TEST Ⅱ set up sweep magnet Flux is closed by iron planes.

TEST Ⅱ set up sweep magnet

Typical Event Display storage ring top view TPC angle 0°

Typical Event Display TPC angle 12.5° storage ring top view

Typical Event Display TPC angle 25° storage ring top view

Extra Data γ e-e- e+e+ start upstandard start counter We just wanted to see multi-track and to read out all sectors! trigger condition: Tag up start up STC

Typical Event Display TPC angle 0° storage ring top view

Typical Event Display TPC angle 0° storage ring top view

Analysis require more than 4 layers are hit. line fit tracking ( least square )  residual distribution x position : estimated by PRF (PL) y position : center of layer TPC angle : 0° sigma : 176μm 12.5° 371μm 25° 824μm ADC value of pulse peak is used. Time peak ADC Our goal …at least ~300μm  too bad.. Resolution is getting worse as track angle increase.

Analysis y position in layer Anode signal has random fluctuation.  Anode which has large signal drags estimated hit position. true position estimated In previous analysis, y position was fixed. (center of layer) y position also have to be estimated.  using anode information true position

Analysis using anode signal y position = center of gravity of charge induced by 5 anode wires = ∑y i * w i * ADC i ( i = 1~5) w 1 = w 5 = , w 2 = w 4 = , w 3 = not using layer1 no field cage  Electric field may be distorted. calibration of anode using cosmic ray data ( taken after beam time ended ). Actually, anode 1 & 27 (most outside) have lower gain in calibration data.

TPC angle : 0° sigma : 175μm 12.5° 196μm 25° 382μm (176μm) (371μm)(824μm) Analysis Resolution is improved.

Analysis Comparison with Gaussian PRF 175μm 196μm 382μm 192μm 197μm 383μm 25° 12.5° 0° Pseudo Lorentzian Gaussian TPC angle Pseudo Lorentzian is slightly better…

Intrinsic resolution require 5 layers are hit residual distribution in the middle layer. track including and excluding the middle layer σexc = 5454 σ σinc = 4545 σ σ= σinc * σexc 0° 133μm 12.5°163μm 25° 331μm intrinsic resolution

Next X-Y position resolution was improved by using anode information, but is still over 300μm.  further analysis Study of Z-direction drift velocity, position resolution, dependence on dip angle … We are waiting for completed new TPC ! DAQ collector has to be arranged for new FADC. ( The number of channel is different. 32ch  16ch )

Convention x y