1. Neutron Structure Functions and a Radial Time Projection Chamber The Structure of the Neutron The BoNuS Experiment at CLAS A New Proton Recoil Detector for CLAS 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Stephen Bültmann Old Dominion University for the BoNuS Collaboration

2. Neutron Structure Function F 2 n Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Proton structure function F 2 p measured very accurately Neutron structure function F 2 n is obtained from measurements on bound neutrons, e.g. using deuterium targets Extraction of F 2 n at large x Bj introduces theoretical model dependence on nuclear corrections (Fermi motion, nucleon offshell corrections, FSI, …) F 2 n 1 + 4 d/u F 2 p 4 + d/u ≈ at leading order and for x Bj > 0.4

3. BoNuS in a Nutshell (CLAS) Measurement of the structure function F 2 n on nearly free neutrons in the reaction e - d  e - p X by measuring the slowly backward moving recoil proton with momentum below 100 MeV/c (suppress FSI and uncertainties from on-shell extrapolation) Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Cut1: p s > 60 MeV/c Cut2: p s 110° Cut3: recoil detector acceptance Simulated event count for 20 days of data taking at 6 GeV

4. Final State Interactions Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 DIS ratio of neutron momentum distributions including FSI to PWIA Calculation at Q 2 = 5 (GeV/c ) 2 and x Bj = 0.2 Small effect for spectator momenta below 100 MeV/c and backward scattering angles C. Ciofi degli Atti, L.P. Kaptari, B.Z. Kopeliovich, Eur. Phys. J. A19, 145 (2004)

5. Experiment E6 in CLAS CLAS presently limited to spectator proton momenta > 280 MeV/c Scattering angle 10° <  < 140° Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 A. Klimenko

6. The BoNuS Experiment Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Long deuterium gas target Long deuterium gas target (spectator protons have to leave target) Large acceptance coverage including backward angles Large acceptance coverage including backward angles Measure momentum by tracking in solenoidal magnetic field around target region (spectator momenta to around 70 MeV/c) Measure momentum by tracking in solenoidal magnetic field around target region (spectator momenta to around 70 MeV/c) Measure energy deposit for particle identification Measure energy deposit for particle identification (spectator protons are 20 to 50 times minimum ionizing) Detector needs to measure high rates Detector needs to measure high rates Main background from Møller electrons Main background from Møller electrons (new solenoid will curl up electrons up to 20 MeV, the higher momentum electron will miss the detector) Measurement at 4 and 6 GeV electron beam energy Measurement at 4 and 6 GeV electron beam energy Expected trigger rate below 1 kHz Expected trigger rate below 1 kHz

7. Conceptual Design of BoNuS RTPC Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 H. Fenker

8. The BoNuS Recoil Detector Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Radial Time Projection Chamber (RTPC) Radial Time Projection Chamber (RTPC) Covering target region Covering target region Gas Electron Multipliers (GEM’s) instead of wires allows new curved geometry Gas Electron Multipliers (GEM’s) instead of wires allows new curved geometry Drift time over 2 cm drift region about 2 µ sec Drift time over 2 cm drift region about 2 µ sec Strip or pad readout Strip or pad readout

9. Gas Electron Multiplier (GEM) Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 F. Sauli, NIM A386, 531 (1997) 50 µm 5 µm 55 µm 70 µm Thin polymer foil (Kapton, APICAL) covered on both sides with conductive (copper) layer Double-conical holes by lithography and chemical etching High electric field (kV/cm) through hole when applying 300 - 500 V potential difference between the two copper layers Gain >100 per GEM

10. Amplification with Multi-GEM’s Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 B. Ketzer, VIC 2004 Cascading GEM foils  Suppress ion feedback  Increase gain up to 10 7 with three GEM’s  Operate GEM’s at lower differential voltage

11. Field Calculation for Curved GEM’s Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Radius 60 mm Electric field does not change significantly

12. Planar Prototype TPC The planar prototype TPC with two new GEM foils of gain >100 at JLab Using initially three standard 10 x 10 cm 2 GEM foils from 3M Corp. with gain ~30 Tests with cosmic rays, x-ray sources, and ~100 MeV/c protons at TUNL Tests with cosmic rays, x-ray sources, and ~100 MeV/c protons at TUNL Readout plane with eight strips Readout plane with eight strips Ar (80) / CO 2 (20) drift gas Ar (80) / CO 2 (20) drift gas Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

13. Test of Planar Prototype TPC Using slow 100 MeV/c secondary protons at TUNL Using slow 100 MeV/c secondary protons at TUNL Protons entering TPC straight Protons entering TPC straight Energy deposit mostly on one strip Energy deposit mostly on one strip Drift [25 nsec] Integrated Charge Strip Number p+p+ Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

14. Planar Prototype TPC at TUNL Strip Number Drift [25 nsec] Integrated Charge Drift [25 nsec] p+p+ Tilted TPC sidewise  protons entering TPC under angle Tilted TPC sidewise  protons entering TPC under angle Energy deposit mostly on several strips, track reconstruction possible Energy deposit mostly on several strips, track reconstruction possible Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

15. Prototype RTPC Drift Region Radial coverage 105° and 10 cm length (determined by GEM foil dimension) Radial coverage 105° and 10 cm length (determined by GEM foil dimension) Entrance window 25  m with etched ground and cathode planes Entrance window 25  m with etched ground and cathode planes Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

16. Prototype RTPC GEM Foil Plane Built three GEM foil planes using standard 10 x 10 cm 2 GEM foil from 3M Corp. Built three GEM foil planes using standard 10 x 10 cm 2 GEM foil from 3M Corp. GEM foils with gain >100 GEM foils with gain >100 (compared to previous 3M Corp. GEM foils with gain ~30) One of three GEM foil planes for prototype RTPC after gluing at ODU Successful high voltage test of GEM to 400 V Successful high voltage test of GEM to 400 V Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

17. Prototype RTPC Assembly Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Readout plane with 8 x 8 pads of 4 x 5 mm 2 size Readout plane with 8 x 8 pads of 4 x 5 mm 2 size (compared to strip readout of planar prototype TPC) (compared to strip readout of planar prototype TPC)

18. BoNuS Readout Electronics Using ALICE TPC R/O electronics from CERN Using ALICE TPC R/O electronics from CERN Dynamic range 900:1 (up to 30 MIP energy loss) Dynamic range 900:1 (up to 30 MIP energy loss) 5 MHz sampling rate 5 MHz sampling rate Features ALTRO chip Features ALTRO chip 16 channels 16 channels 10 bit A/D conversion 10 bit A/D conversion Baseline subtraction and zero suppression Baseline subtraction and zero suppression Digital processing and event buffering Digital processing and event buffering Expects positive input signal  need signal charge conversion on input Expects positive input signal  need signal charge conversion on input Eight ALTRO chips per FEC  128 input channels Eight ALTRO chips per FEC  128 input channels Need 32 FEC’s for 4,096 readout pads Need 32 FEC’s for 4,096 readout pads FEC’s interconnected via readout controller card FEC’s interconnected via readout controller card (new version featuring USB port available to us at the end of March) Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

19. ALICE TPC Front End Card + Bus Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Readout board for 128 channels Readout board for 128 channels Custom integration into CLAS Custom integration into CLAS Readout electronics can be used for TPC of different geometry Readout electronics can be used for TPC of different geometry

20. CLAS with Møller Solenoid and BoNuS Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

21. BoNuS Detector Inside Møller Solenoid Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 H. Fenker

22. Timeline for the BoNuS Experiment Spring 2004 Construction and testing of prototype RTPC with test run at TUNL in April Construction and testing of prototype RTPC with test run at TUNL in April Autumn 2004 Ready for test run of prototype RTPC in conjunction with DVCS experiment Ready for test run of prototype RTPC in conjunction with DVCS experiment2005 Build RTPC to be ready in summer Build RTPC to be ready in summer Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004

23. Structure Functions at 11 GeV Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Uncertainty band due to different treatment of nuclear effects Two measurements planned Low momentum range Low momentum range 70 - 100 MeV/c backward moving spectator nucleon 70 - 100 MeV/c backward moving spectator nucleon (BoNuS recoil detector + CLAS++) Luminosity 5 · 10 33 cm -2 sec -1 Luminosity 5 · 10 33 cm -2 sec -1 x Bj < 0.8 x Bj < 0.8 5% measurement of F 2 n in 40 days 5% measurement of F 2 n in 40 days High momentum range High momentum range 250 - 700 MeV/c (upgraded CLAS++) 250 - 700 MeV/c (upgraded CLAS++) Luminosity 10 35 cm -2 sec -1 Luminosity 10 35 cm -2 sec -1 Standard liquid deuterium target Standard liquid deuterium target

24. Structure Functions at 11 GeV Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004  Cover large kinematical range electron (x Bj and Q 2 ) and recoil proton (p T and  S )  High momentum measurement  20 days of data taking

25. Neutron Structure Function at eRHIC Stephen Bültmann - ODU 2 nd EIC Workshop at Jefferson Lab, March 15 - 17, 2004 Very large kinematic range Very large kinematic range Measure spectator proton at almost zero initial momentum (half of the deuteron momentum in EIC frame) Measure spectator proton at almost zero initial momentum (half of the deuteron momentum in EIC frame) Do not need to measure slow recoil protons Do not need to measure slow recoil protons