IHEP-BINP CEPC accelerator collaboration workshop Beam energy calibration without polarization

Transcription

1 IHEP-BINP CEPC accelerator collaboration workshop Beam energy calibration without polarization Nickolai Muchnoi Budker INP, Novosibirsk January 12, 2016 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

2 TALK OUTLINE 1 Introduction 2 Energy scale calibration 3 BEMS 2015 test 4 Extending beam energy range? 5 Conclusion Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

3 Introduction The energy released in the annihilation of an electron and positron is an important property: it establishes kinematic bounds for any processes under investigation. The processes with resonance or threshold cross section dependence on the c.m.s. energy allow accurate determination of particle masses. World-wide experience shows that beam energy calibration usually consumes additional time and eorts. For future high energy colliders it is necessary to accumulate and extend the experience gathered at low energy machines. Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

4 BEPC-II Beam Energy Measurement System (BEMS) Project was started in 2008 First tests and ψ(2s) scan December, 2010 τ mass measurement experiment December, 2011 Continuous operation, 1MeV problem 2012 Malfunction of the laser 2013 Laser repair, new ZnSe vacuum windows BEMS beam test with a new laser May, 2015 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

5 Inverse Compton Scattering electron: ε0, γ=ε 0 /m photon: ω electron: ε θ ω θ ε photon: ω 0 Scattering parameters are u and κ: u = ω ε = θ ε θ ω = ω ε 0 ω ; u [0, κ] ; κ = 4ω 0ε 0 m 2. Scattering angles: γθ ω = κ/u 1; γθ ε = u κ/u 1. Maximum energy of scattered photon (θ ω = θ ε = 0): ω max = ε 0κ 1 + κ. ( ) Initial electron energy: ε 0 = ω max m2 m ωmax. 2 ω 0 ω max 2 ω 0 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

6 Accurate energy scale transfer: ev MeV GeV IR optics, 10P20 CO 2 laser line: ω 0 = ev γ-lines from excited nuclei as a good reference for ω max : 137 Cs τ 1/ y E γ = ± kev 60 Co τ 1/ y E γ = ± kev E γ = ± kev 208 Tl τ 1/2 3 m E γ = ± kev 16 O E γ = ± kev High energy physics scale 1 : J/ψ ± ± MeV ψ(2s) ± ± MeV 1 Final analysis of KEDR data, Physics Letters B 749 (2015) Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

7 BEMS layout at the North BEPC I.P. positrons electrons R2IAMB HPGe R1IAMB 2.5m 3.25m 3.75m m 0.4m Laser Lenses Size of HPGe detector D 4 cm Distance between HPGe and γe + /γe scattering area L 8 m Beam orbit angle should be zero within θ D/L ±2.5 mrad If θ is outside these limits, measurements are impossible! THIS IS 1 BEMS PROBLEM: NO DATA = NO MEASUREMENT! Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

8 BEMS SUBSYSTEMS Laser & optics system provides laser transportation and necessary focusing to the interaction area. Control system provides change of laser direction to electron or positron beam, control over additional moving shield 2, tune (maximize) the rate of backscattered photons. It uses DAQ system counting rates as a feedback signal. DAQ system reads HPGe data from MCA, saves the raw data to disk. Uses Control system status to distinguish electron/positron records. ALL RAW DATA IS AVAILABLE! On-line analysis system provides online beam energy determination results and writes them to the BEPC database. O-line analysis role is to make various checks and get better results. 2 Up to 18 cm of lead shielding was installed to suppress beam background! Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

9 1 Introduction 2 Energy scale calibration 3 BEMS 2015 test 4 Extending beam energy range? 5 Conclusion Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

10 Absolute energy measurements by HPGe spectrometers Practical experience has been gained in the eld of nuclear spectroscopy. Idaho group recommendations for precise absolute measurements: use more than one spectrometer simultaneous and unidirectional measurement of calibration lines and energies under investigation perform energy calibration in a narrow range instead of polynomial extrapolation of the whole scale avoid using m 0 c 2 or 2m 0 c 2 values for determination of energy dierence between photo-peak and escape-peaks avoid using pulsers for calibration Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

11 Our approach is dierent cause the range where we work is rather wide. So we will try to: nd an appropriate function to describe the total total absorption peak shape; check that the parameters of this function have a smooth energy dependence; use BNC PB-5 precise amplitude pulser with declared integral linearity as small as 15 ppm. Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

12 HPGe energy response function Amplitude [a.u.] gauss another gauss exponent tail Compton edge (ω-ω 0 ) in units of σ Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

13 HPGe energy response function 0 < x < + : exp { x2 } 2σ 2 f(x) = A K 0 K 1 σ < x 0 : C + (1 C) exp { x2 } { 2(K ( 0 σ) 2 x < x K 0 K 1 σ : C + (1 C) exp K 1 K 0 σ + K )} 1 2 A amplitude, x = 0 line energy, σ normal width, K 0 σ width from-the-left modication, K 1 K 0 σ exponential low-energy tail, C is for low-angle scattering of γ-s on their way to detector. Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

14 6129 kev peak (2011 data) O ( kev) χ 2 /ndf = 61.8/ E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

15 HPGe energy resolution (2011 data) σ E = σ εf E ε electron-hole creation energy in Ge, F Fano factor 0.25 / E, % σ E 0.20 reference lines pulser lines other lines E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

16 Peak shape widening, K 0 (K 1 = ) K 0 1.6, K, Compton 1 K 0 Compton,% E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

17 Wide-range scale calibration E FIT - E REF, kev 0.2 reference lines pulser lines other lines Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

18 1 Introduction 2 Energy scale calibration 3 BEMS 2015 test 4 Extending beam energy range? 5 Conclusion Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

19 BEMS test in May, 2015: spectrum example Electrons: [09:08:46 10:44:12] Live time: 0 hours 44 min 20 s E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

20 BEMS test in May, 2015: calibration lines t Cs ( kev) χ /ndf = 58.5/ Co ( kev) χ /ndf = 65.8/68 60 Co ( kev) χ 2 /ndf = 86.2/ E γ, kev E γ, kev E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

21 BEPC orbit inuence example: GOOD (e ) & BAD (e + ) Electrons: [08:50:05 09:02:07] Live time: 0 hours 7 min 43 s Positrons: [09:32:09 09:43:28] Live time: 0 hours 4 min 32 s E γ, kev E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

22 Edge Fit 600 K = 1: χ 2 0 /NDF = 314.2/ ω max = ± 0.15 kev 400 what happens if K = Electrons: [00:05:25-00:17:27] Live-time: 0 hours 7 min 32 s E γ, kev K 0 = 1.48 ± 0.15: χ /NDF = 304.3/295 ω max = ± 0.15 ± 0.22 kev E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

23 Copy of tting output Simple Edge Fit: Range from to kev E_beam = MeV W_max = kev Edge amplitude : ± Edge slope: ± Edge wmax, kev: ± Backgrond level: ± Edge width, kev: ± Background slope: ± χ2/ndf = 314.2/307 Probability: Complex Edge Fit: Range from to kev Amplitude = W_max = kev HPGe resolution = kev HPGe K0 = Spread = kev Edge wmax: ± 0.15 ± 0.22 kev Beam σe impact: 2.73 ± 0.28 ± 0.18 kev Edge amplitude : ± Backgrond level: ± HPGe resol, kev: ± Background slope: ± HPGe K0 : ± Compton slope: ± χ2/ndf = 304.3/295 Probability: Wmax: ± 0.15 kev (symmetric fit) Wmax: ± 0.26 kev (asymmetric fit) Wmax: ± 0.32 kev (linear scale error) Wmax: ± 0.32 kev (spline correction ) electron Beam Energy Determination: BEPC beam energy = ± MeV was taken from database Measurement time from :05:25 to :17:27. BEMS beam energy = ± MeV (SR correction to IP MeV was added) BEMS beam spread = 682 ± 83 kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

24 BEMS results: electron beam energy. E 1.5 MeV Beam energy, MeV BEPC energy: electron beam BEMS energy: electron beam χ / ndf / 237 p ± May 01 06:00 May 01 18:00 May 02 06:00 May 02 18:00 May 03 06:00 May 03 18:00 May 04 06:00 May 04 18:00 May 05 06:00 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

25 BEMS results: positron beam energy. E 0.9 MeV Beam energy, MeV BEPC energy: positron beam χ 2 / ndf / 212 p ± BEMS energy: positron beam May 01 06:00 May 01 18:00 May 02 06:00 May 02 18:00 May 03 06:00 May 03 18:00 May 04 06:00 May 04 18:00 May 05 06:00 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

26 Orbit radius oscillations (BPR) from signal Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

27 Orbit radius oscillations (BER) from signal Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

28 Orbit radius oscillations (BER) from signal Most probable explanation for the observed oscillations is the oscillations in BEPC guide eld, where frequencies are the multiples of AC line frequency. If so, this denitely leads to average energy oscillations. Long-time average distribution of the electrons energies is no more a Normal distribution. If so, the edge tting procedure becomes incorrect, leading to systematic shift of results. We are going to implement direct eld oscillations measurement by induction probes. Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

29 1 Introduction 2 Energy scale calibration 3 BEMS 2015 test 4 Extending beam energy range? 5 Conclusion Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

30 LASER BEAM Spectrometer with laser calibration DIPOLE MAGNET Compton photons X 0 electron beam Compton electrons with min. energy θ X beam Here tiny fraction of the beam electrons are scattered on the laser wave L Δθ X edge Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

31 LASER BEAM Spectrometer with laser calibration θ θ = κ = 4ω 0E 0 m 2 DIPOLE MAGNET Compton photons X 0 electron beam Compton electrons with min. energy θ X beam Here tiny fraction of the beam electrons are scattered on the laser wave L Δθ X edge Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

32 LASER BEAM Spectrometer with laser calibration θ θ = κ = 4ω 0E 0 m 2 DIPOLE MAGNET Compton photons X 0 electron beam Compton electrons with min. energy θ X beam Here tiny fraction of the beam electrons are scattered on the laser wave L Δθ X edge Access to the beam energy: E 0 = θ θ m2 4ω 0 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

33 LASER BEAM Spectrometer with laser calibration E 0 =100 GeV, ω 0 =1 ev: θ θ 1.53 DIPOLE MAGNET Here tiny fraction of the beam electrons are scattered on the laser wave Compton photons electron beam Compton electrons with min. energy L Δθ θ X 0 X beam X edge Access to the beam energy: E 0 = θ θ m2 4ω 0 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

34 Use of 2D pixel detector for scattered electrons? κ = 3.26, ϑ ϑ X = 500, P = [ 0.0, 0.0, -0.5, 0.0 ] HD Entries 1e+07 χ 2 / ndf 2662 / 2709 X ± X ± σ X ± Y ± Y ± σ Y ± P 0.5 ± P ± norm 1.735e+06 ± ϑ Y Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

35 Energy of scattered electrons? E min = E/(1 + 4ω 0E m 2 ) min electron energy, GeV ω 0 =0.120 ev ω 0 =1.165 ev ω 0 =2.330 ev ω 0 =4.660 ev beam energy, GeV Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

36 1 Introduction 2 Energy scale calibration 3 BEMS 2015 test 4 Extending beam energy range? 5 Conclusion Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34

37 Conclusion Beam energy calibration extends the eld of possible physics. BEPC-II has the Beam Energy Measurement System (since 2010). BEMS operation should be studied and understood by IHEP accelerator community cause many of relevant problems are energy independent. The low-energy experience should be accumulated and used for future collider projects. As for CEPC and other high energy machines some ideas exist already and should be studied in details. THANK YOU! Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, / 34