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, 2016 1 / 34
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, 2016 2 / 34
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, 2016 3 / 34
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 - 2014 BEMS beam test with a new laser May, 2015 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 4 / 34
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 1 + 1 + m2 m ωmax. 2 ω 0 ω max 2 ω 0 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 5 / 34
Accurate energy scale transfer: ev MeV GeV IR optics, 10P20 CO 2 laser line: ω 0 = 0.117065228 ev γ-lines from excited nuclei as a good reference for ω max : 137 Cs τ 1/2 30.07 y E γ = 0661.657 ± 0.003 kev 60 Co τ 1/2 5.27 y E γ = 1173.228 ± 0.003 kev E γ = 1332.422 ± 0.004 kev 208 Tl τ 1/2 3 m E γ = 2614.511 ± 0.013 kev 16 O E γ = 6129.266 ± 0.054 kev High energy physics scale 1 : J/ψ 3096.900 ± 0.002 ± 0.006 MeV ψ(2s) 3686.099 ± 0.004 ± 0.009 MeV 1 Final analysis of KEDR data, Physics Letters B 749 (2015) 50-56 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 6 / 34
BEMS layout at the North BEPC I.P. positrons electrons R2IAMB HPGe R1IAMB 2.5m 3.25m 3.75m 0000000000000000 1111111111111111 11111111110000000000 6.0m 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, 2016 7 / 34
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, 2016 8 / 34
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, 2016 9 / 34
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, 2016 10 / 34
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, 2016 11 / 34
HPGe energy response function Amplitude [a.u.] 1.0 0.8 0.6 0.4 gauss another gauss exponent tail Compton edge 0.2 0.0-6 -4-2 0 2 4 (ω-ω 0 ) in units of σ Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 12 / 34
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, 2016 13 / 34
6129 kev peak (2011 data) 16 1000 O (6129.266 kev) χ 2 /ndf = 61.8/82 950 900 850 800 750 700 650 600 6100 6105 6110 6115 6120 6125 6130 6135 6140 6145 E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 14 / 34
HPGe energy resolution (2011 data) σ E = σ 2 0 + 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 0.15 0.10 0.05 0.00 1000 2000 3000 4000 5000 6000 E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 15 / 34
Peak shape widening, K 0 (K 1 = ) K 0 1.6, K, Compton 1 K 0 Compton,% 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 500 1000 1500 2000 2500 E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 16 / 34
Wide-range scale calibration E FIT - E REF, kev 0.2 reference lines pulser lines other lines 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1000 2000 3000 4000 5000 6000 Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 17 / 34
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, 2016 18 / 34
BEMS test in May, 2015: spectrum example Electrons: 2015.05.01 [09:08:46 10:44:12] 2015.05.01. Live time: 0 hours 44 min 20 s. 18000 16000 14000 12000 10000 8000 6000 4000 2000 0 500 1000 1500 2000 2500 3000 E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 19 / 34
BEMS test in May, 2015: calibration lines t 137 2 Cs (661.657 kev) χ /ndf = 58.5/54 60 2 Co (1173.228 kev) χ /ndf = 65.8/68 60 Co (1332.492 kev) χ 2 /ndf = 86.2/74 4000 3500 3000 2500 4500 4000 3500 3000 4000 3500 3000 2000 2500 2500 1500 1000 650 655 660 665 670 E γ, kev 2000 1500 1155 1160 1165 1170 1175 1180 1185 E γ, kev 2000 1500 1315 1320 1325 1330 1335 1340 1345 E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 20 / 34
BEPC orbit inuence example: GOOD (e ) & BAD (e + ) Electrons: 2015.05.04 [08:50:05 09:02:07] 2015.05.04. Live time: 0 hours 7 min 43 s. 6000 5000 4000 3000 2000 Positrons: 2015.05.04 [09:32:09 09:43:28] 2015.05.04. Live time: 0 hours 4 min 32 s. 14000 12000 10000 8000 6000 4000 1000 2000 0 500 1000 1500 2000 2500 3000 E γ, kev 0 500 1000 1500 2000 2500 3000 E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 21 / 34
Edge Fit 600 K = 1: χ 2 0 /NDF = 314.2/307 500 ω max = 2231.69 ± 0.15 kev 400 what happens if K = 1.48 0 300 Electrons: 2015.05.01 [00:05:25-00:17:27] 2015.05.01. Live-time: 0 hours 7 min 32 s. 200 100 2200 2210 2220 2230 2240 2250 2260 2270 2280 E γ, kev 600 500 400 2 K 0 = 1.48 ± 0.15: χ /NDF = 304.3/295 ω max = 2232.69 ± 0.15 ± 0.22 kev 300 200 100 2200 2210 2220 2230 2240 2250 2260 2270 2280 E γ, kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 22 / 34
Copy of tting output Simple Edge Fit: Range from 2126.8 to 2356.2 kev E_beam = 1119.13 MeV W_max = 2241.506 kev Edge amplitude : 511.271 ± 5.3719 Edge slope: 0.078 ± 0.0812 Edge wmax, kev: 2231.694 ± 0.1519 Backgrond level: 92.455 ± 1.7183 Edge width, kev: 4.368 ± 0.1832 Background slope: -0.069 ± 0.0227 χ2/ndf = 314.2/307 Probability: 0.376 Complex Edge Fit: Range from 2117.1 to 2346.3 kev Amplitude = 511.3 W_max = 2231.694 kev HPGe resolution = 2.764 kev HPGe K0 = 1.478 Spread = 3.383 kev Edge wmax: 2232.69 ± 0.15 ± 0.22 kev Beam σe impact: 2.73 ± 0.28 ± 0.18 kev Edge amplitude : 502.029 ± 4.6094 Backgrond level: 92.455 ± 0.0000 HPGe resol, kev: 2.764 ± 0.0000 Background slope: -0.069 ± 0.0000 HPGe K0 : 1.478 ± 0.0000 Compton slope: -0.001 ± 0.0013 χ2/ndf = 304.3/295 Probability: 0.342 Wmax: 2231.69 ± 0.15 kev (symmetric fit) Wmax: 2232.69 ± 0.26 kev (asymmetric fit) Wmax: 2232.69 ± 0.32 kev (linear scale error) Wmax: 2233.43 ± 0.32 kev (spline correction ) electron Beam Energy Determination: BEPC beam energy = 1119.132 ± 0.146 MeV was taken from database Measurement time from 2015.05.01 00:05:25 to 2015.05.01 00:17:27. BEMS beam energy = 1117.119 ± 0.080 MeV (SR correction to IP +0.007 MeV was added) BEMS beam spread = 682 ± 83 kev Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 23 / 34
BEMS results: electron beam energy. E 1.5 MeV Beam energy, MeV 1065.4 1065.2 1065.0 BEPC energy: electron beam BEMS energy: electron beam 1064.8 1064.6 2 χ / ndf 59.605 / 237 p0 1063.965 ± 0.007 1064.4 1064.2 1064.0 1063.8 1063.6 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, 2016 24 / 34
BEMS results: positron beam energy. E 0.9 MeV Beam energy, MeV 1065.2 1065.0 1064.8 BEPC energy: positron beam χ 2 / ndf 47.650 / 212 p0 1064.186 ± 0.014 BEMS energy: positron beam 1064.6 1064.4 1064.2 1064.0 1063.8 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, 2016 25 / 34
Orbit radius oscillations (BPR) from signal Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 26 / 34
Orbit radius oscillations (BER) from signal Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 27 / 34
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, 2016 28 / 34
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, 2016 29 / 34
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, 2016 30 / 34
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, 2016 30 / 34
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, 2016 30 / 34
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, 2016 30 / 34
Use of 2D pixel detector for scattered electrons? 40000 35000 30000 25000 20000 15000 10000 5000 0 κ = 3.26, ϑ 0 0 200 400 600 8001000120014001600 ϑ X = 500, P = [ 0.0, 0.0, -0.5, 0.0 ] HD Entries 1e+07 χ 2 / ndf 2662 / 2709 X 1 0.1313 ± 0.1649 X 2 1630 ± 0.06344 σ X 21.62 ± 0.05565 Y 1 1.63 ± 0.0001923 Y 2 1.63 ± 0.0001942 σ Y 0.1045 ± 0.0001082 P 0.5 ± 0.00103 P 0.0005721 ± 0.002095 norm 1.735e+06 ± 772.3 1.5 2 2 1.5 1 0.5 0 0.51 ϑ Y Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 31 / 34
Energy of scattered electrons? E min = E/(1 + 4ω 0E m 2 ) min electron energy, GeV 120 100 80 60 40 20 ω 0 =0.120 ev ω 0 =1.165 ev ω 0 =2.330 ev ω 0 =4.660 ev 0 40 50 60 70 80 90 100 110 120 beam energy, GeV Nickolai Muchnoi IHEP-BINP CEPC workshop January 12, 2016 32 / 34
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, 2016 33 / 34
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, 2016 34 / 34