ASPECTS ON THE COLD BPM S IN THE MAIN LINAC

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1 ASPECTS ON THE COLD BPM S IN THE MAIN LINAC 1. Resoluton 2. Resoluton 3. Resoluton Manfred Wendt, Fermlab manfred@fnal.gov 1/15 < >

2 Contents INTRODUCTION BPM ASPECTS CANDIDATES FOR COLD BPM PICKUP S CONCLUSIONS 2/15 < >

3 INTRODUCTION Dedcated BPM s and HOM coupler sgnals for beam poston measurements n the man lnac. 3/15 < >

4 The bunch-tran s the stmulus sgnal for the BPM system (not to scale). The tme resoluton of the BPM system has to be defned, e. g. should be able to resolve the beam poston of any/every sngle bunch n the bunch-tran: τ BPM < t B The poston resoluton mproves by averagng the n B sngle-bunch postons: Resoluton multbunch Resoluton snglebunch nb whch s equvalent to reducng the bandwdth of the BPM system. 4/15 < >

5 The bunch-tran s the stmulus sgnal for the BPM system (not to scale). The tme resoluton of the BPM system has to be defned, e. g. should be able to resolve the beam poston of any/every sngle bunch n the bunch-tran: τ BPM < t B The poston resoluton mproves by averagng the n B sngle-bunch postons: Resoluton multbunch Resoluton snglebunch nb whch s equvalent to reducng the bandwdth of the BPM system. 4/15 < >

6 The bunch-tran s the stmulus sgnal for the BPM system (not to scale). The tme resoluton of the BPM system has to be defned, e. g. should be able to resolve the beam poston of any/every sngle bunch n the bunch-tran: τ BPM < t B The poston resoluton mproves by averagng the n B sngle-bunch postons: Resoluton multbunch Resoluton snglebunch nb whch s equvalent to reducng the bandwdth of the BPM system. 4/15 < >

7 BPM ASPECTS Requrements A clear defned set of BPM requrements s mandatory; and t has to be kept up to date(!). The RMS poston resoluton of the BPM pckup or complete system (. e. wth read-out electroncs) n a specfed ntegraton (measurement) tme; e. g. 10 µm SB, 1 µm BT (). The transverse measurement range to be covered; e. g. ± µm SB res. (). Specfy extended ranges wth reduced resoluton; e. g. > µm SB res. (). Nomnal beam/bunch ntenstes, e. g nc/bunch (). Defnes the dynamc range of the read-out electroncs. The BPM system wll have a reduced resoluton at lower ntense beams(!). Lnearty and orthogonalty,. e. cross-talk between horzontal and vertcal axs; e. g. < 2 ± 15 mm (). Systematc nonlneartes of the BPM pckup can be lnearzed by 2D feld mappng procedures. Absolute precson and reproducblty, after a temperature cycle of the cryostat, etc.; e. g. < 200 µm (). 5/15 < >

8 BPM ASPECTS Requrements A clear defned set of BPM requrements s mandatory; and t has to be kept up to date(!). The RMS poston resoluton of the BPM pckup or complete system (. e. wth read-out electroncs) n a specfed ntegraton (measurement) tme; e. g. 10 µm SB, 1 µm BT (). The transverse measurement range to be covered; e. g. ± µm SB res. (). Specfy extended ranges wth reduced resoluton; e. g. > µm SB res. (). Nomnal beam/bunch ntenstes, e. g nc/bunch (). Defnes the dynamc range of the read-out electroncs. The BPM system wll have a reduced resoluton at lower ntense beams(!). Lnearty and orthogonalty,. e. cross-talk between horzontal and vertcal axs; e. g. < 2 ± 15 mm (). Systematc nonlneartes of the BPM pckup can be lnearzed by 2D feld mappng procedures. Absolute precson and reproducblty, after a temperature cycle of the cryostat, etc.; e. g. < 200 µm (). 5/15 < >

9 BPM ASPECTS Requrements A clear defned set of BPM requrements s mandatory; and t has to be kept up to date(!). The RMS poston resoluton of the BPM pckup or complete system (. e. wth read-out electroncs) n a specfed ntegraton (measurement) tme; e. g. 10 µm SB, 1 µm BT (). The transverse measurement range to be covered; e. g. ± µm SB res. (). Specfy extended ranges wth reduced resoluton; e. g. > µm SB res. (). Nomnal beam/bunch ntenstes, e. g nc/bunch (). Defnes the dynamc range of the read-out electroncs. The BPM system wll have a reduced resoluton at lower ntense beams(!). Lnearty and orthogonalty,. e. cross-talk between horzontal and vertcal axs; e. g. < 2 ± 15 mm (). Systematc nonlneartes of the BPM pckup can be lnearzed by 2D feld mappng procedures. Absolute precson and reproducblty, after a temperature cycle of the cryostat, etc.; e. g. < 200 µm (). 5/15 < >

10 BPM ASPECTS Requrements A clear defned set of BPM requrements s mandatory; and t has to be kept up to date(!). The RMS poston resoluton of the BPM pckup or complete system (. e. wth read-out electroncs) n a specfed ntegraton (measurement) tme; e. g. 10 µm SB, 1 µm BT (). The transverse measurement range to be covered; e. g. ± µm SB res. (). Specfy extended ranges wth reduced resoluton; e. g. > µm SB res. (). Nomnal beam/bunch ntenstes, e. g nc/bunch (). Defnes the dynamc range of the read-out electroncs. The BPM system wll have a reduced resoluton at lower ntense beams(!). Lnearty and orthogonalty,. e. cross-talk between horzontal and vertcal axs; e. g. < 2 ± 15 mm (). Systematc nonlneartes of the BPM pckup can be lnearzed by 2D feld mappng procedures. Absolute precson and reproducblty, after a temperature cycle of the cryostat, etc.; e. g. < 200 µm (). 5/15 < >

11 BPM ASPECTS Requrements A clear defned set of BPM requrements s mandatory; and t has to be kept up to date(!). The RMS poston resoluton of the BPM pckup or complete system (. e. wth read-out electroncs) n a specfed ntegraton (measurement) tme; e. g. 10 µm SB, 1 µm BT (). The transverse measurement range to be covered; e. g. ± µm SB res. (). Specfy extended ranges wth reduced resoluton; e. g. > µm SB res. (). Nomnal beam/bunch ntenstes, e. g nc/bunch (). Defnes the dynamc range of the read-out electroncs. The BPM system wll have a reduced resoluton at lower ntense beams(!). Lnearty and orthogonalty,. e. cross-talk between horzontal and vertcal axs; e. g. < 2 ± 15 mm (). Systematc nonlneartes of the BPM pckup can be lnearzed by 2D feld mappng procedures. Absolute precson and reproducblty, after a temperature cycle of the cryostat, etc.; e. g. < 200 µm (). 5/15 < >

12 BPM ASPECTS Requrements A clear defned set of BPM requrements s mandatory; and t has to be kept up to date(!). The RMS poston resoluton of the BPM pckup or complete system (. e. wth read-out electroncs) n a specfed ntegraton (measurement) tme; e. g. 10 µm SB, 1 µm BT (). The transverse measurement range to be covered; e. g. ± µm SB res. (). Specfy extended ranges wth reduced resoluton; e. g. > µm SB res. (). Nomnal beam/bunch ntenstes, e. g nc/bunch (). Defnes the dynamc range of the read-out electroncs. The BPM system wll have a reduced resoluton at lower ntense beams(!). Lnearty and orthogonalty,. e. cross-talk between horzontal and vertcal axs; e. g. < 2 ± 15 mm (). Systematc nonlneartes of the BPM pckup can be lnearzed by 2D feld mappng procedures. Absolute precson and reproducblty, after a temperature cycle of the cryostat, etc.; e. g. < 200 µm (). 5/15 < >

13 Mechancal and Envronmental Aspects Besde the usual mechancal and vacuum aspects, the operaton of the BPM pckup detector n a cryogenc, cleanroom approved envronment requres addtonal care: Beam ppe aperture,. e. crcular cross-secton of mm dameter (TESLA: 78 mm). Keep n mnd: The poston resoluton scales wth the beam ppe aperture! Longtudnal and radal space for the BPM pckup. Flange types and locaton, bellows, mountng ssues. RF-sgnal cables n the cryostat (low sgnal losses, hgh temperature solaton). Cryogenc RF vacuum feedthroughs for the pckup sgnals (low VSWR at operaton frequences, UHV stable ceramcs after many temperature cycles). Cleanable and cleanroom (class ) approved BPM pckup constructon. 6/15 < >

14 Mechancal and Envronmental Aspects Besde the usual mechancal and vacuum aspects, the operaton of the BPM pckup detector n a cryogenc, cleanroom approved envronment requres addtonal care: Beam ppe aperture,. e. crcular cross-secton of mm dameter (TESLA: 78 mm). Keep n mnd: The poston resoluton scales wth the beam ppe aperture! Longtudnal and radal space for the BPM pckup. Flange types and locaton, bellows, mountng ssues. RF-sgnal cables n the cryostat (low sgnal losses, hgh temperature solaton). Cryogenc RF vacuum feedthroughs for the pckup sgnals (low VSWR at operaton frequences, UHV stable ceramcs after many temperature cycles). Cleanable and cleanroom (class ) approved BPM pckup constructon. 6/15 < >

15 Mechancal and Envronmental Aspects Besde the usual mechancal and vacuum aspects, the operaton of the BPM pckup detector n a cryogenc, cleanroom approved envronment requres addtonal care: Beam ppe aperture,. e. crcular cross-secton of mm dameter (TESLA: 78 mm). Keep n mnd: The poston resoluton scales wth the beam ppe aperture! Longtudnal and radal space for the BPM pckup. Flange types and locaton, bellows, mountng ssues. RF-sgnal cables n the cryostat (low sgnal losses, hgh temperature solaton). Cryogenc RF vacuum feedthroughs for the pckup sgnals (low VSWR at operaton frequences, UHV stable ceramcs after many temperature cycles). Cleanable and cleanroom (class ) approved BPM pckup constructon. 6/15 < >

16 Mechancal and Envronmental Aspects Besde the usual mechancal and vacuum aspects, the operaton of the BPM pckup detector n a cryogenc, cleanroom approved envronment requres addtonal care: Beam ppe aperture,. e. crcular cross-secton of mm dameter (TESLA: 78 mm). Keep n mnd: The poston resoluton scales wth the beam ppe aperture! Longtudnal and radal space for the BPM pckup. Flange types and locaton, bellows, mountng ssues. RF-sgnal cables n the cryostat (low sgnal losses, hgh temperature solaton). Cryogenc RF vacuum feedthroughs for the pckup sgnals (low VSWR at operaton frequences, UHV stable ceramcs after many temperature cycles). Cleanable and cleanroom (class ) approved BPM pckup constructon. 6/15 < >

17 Mechancal and Envronmental Aspects Besde the usual mechancal and vacuum aspects, the operaton of the BPM pckup detector n a cryogenc, cleanroom approved envronment requres addtonal care: Beam ppe aperture,. e. crcular cross-secton of mm dameter (TESLA: 78 mm). Keep n mnd: The poston resoluton scales wth the beam ppe aperture! Longtudnal and radal space for the BPM pckup. Flange types and locaton, bellows, mountng ssues. RF-sgnal cables n the cryostat (low sgnal losses, hgh temperature solaton). Cryogenc RF vacuum feedthroughs for the pckup sgnals (low VSWR at operaton frequences, UHV stable ceramcs after many temperature cycles). Cleanable and cleanroom (class ) approved BPM pckup constructon. 6/15 < >

18 Mechancal and Envronmental Aspects Besde the usual mechancal and vacuum aspects, the operaton of the BPM pckup detector n a cryogenc, cleanroom approved envronment requres addtonal care: Beam ppe aperture,. e. crcular cross-secton of mm dameter (TESLA: 78 mm). Keep n mnd: The poston resoluton scales wth the beam ppe aperture! Longtudnal and radal space for the BPM pckup. Flange types and locaton, bellows, mountng ssues. RF-sgnal cables n the cryostat (low sgnal losses, hgh temperature solaton). Cryogenc RF vacuum feedthroughs for the pckup sgnals (low VSWR at operaton frequences, UHV stable ceramcs after many temperature cycles). Cleanable and cleanroom (class ) approved BPM pckup constructon. 6/15 < >

19 Mechancal and Envronmental Aspects Besde the usual mechancal and vacuum aspects, the operaton of the BPM pckup detector n a cryogenc, cleanroom approved envronment requres addtonal care: Beam ppe aperture,. e. crcular cross-secton of mm dameter (TESLA: 78 mm). Keep n mnd: The poston resoluton scales wth the beam ppe aperture! Longtudnal and radal space for the BPM pckup. Flange types and locaton, bellows, mountng ssues. RF-sgnal cables n the cryostat (low sgnal losses, hgh temperature solaton). Cryogenc RF vacuum feedthroughs for the pckup sgnals (low VSWR at operaton frequences, UHV stable ceramcs after many temperature cycles). Cleanable and cleanroom (class ) approved BPM pckup constructon. 6/15 < >

20 Other Aspects Beam couplng mpedance,. e. wake potental of the BPM pckup due to the perturbaton of the beam s EM-feld (adds to the heat load n the cryostat and may cause beam break-up forces n long bunch trans). Assembly and seres producton ssues. Radaton related aspects (cables, connectors, electroncs, etc.) and relablty (MTBF). Costs, number of requred BPM s (TESLA: 2 368). Specal requrements for lnac commssonng, e. g. beam ntensty measurement, lowntense plot bunch orbt observaton (dynamc range!). Data-acquston and transfer aspects, nterface to the control system (fber or copper lnks, data communcaton ndustry standards, etc.).... 7/15 < >

21 Other Aspects Beam couplng mpedance,. e. wake potental of the BPM pckup due to the perturbaton of the beam s EM-feld (adds to the heat load n the cryostat and may cause beam break-up forces n long bunch trans). Assembly and seres producton ssues. Radaton related aspects (cables, connectors, electroncs, etc.) and relablty (MTBF). Costs, number of requred BPM s (TESLA: 2 368). Specal requrements for lnac commssonng, e. g. beam ntensty measurement, lowntense plot bunch orbt observaton (dynamc range!). Data-acquston and transfer aspects, nterface to the control system (fber or copper lnks, data communcaton ndustry standards, etc.).... 7/15 < >

22 Other Aspects Beam couplng mpedance,. e. wake potental of the BPM pckup due to the perturbaton of the beam s EM-feld (adds to the heat load n the cryostat and may cause beam break-up forces n long bunch trans). Assembly and seres producton ssues. Radaton related aspects (cables, connectors, electroncs, etc.) and relablty (MTBF). Costs, number of requred BPM s (TESLA: 2 368). Specal requrements for lnac commssonng, e. g. beam ntensty measurement, lowntense plot bunch orbt observaton (dynamc range!). Data-acquston and transfer aspects, nterface to the control system (fber or copper lnks, data communcaton ndustry standards, etc.).... 7/15 < >

23 Other Aspects Beam couplng mpedance,. e. wake potental of the BPM pckup due to the perturbaton of the beam s EM-feld (adds to the heat load n the cryostat and may cause beam break-up forces n long bunch trans). Assembly and seres producton ssues. Radaton related aspects (cables, connectors, electroncs, etc.) and relablty (MTBF). Costs, number of requred BPM s (TESLA: 2 368). Specal requrements for lnac commssonng, e. g. beam ntensty measurement, lowntense plot bunch orbt observaton (dynamc range!). Data-acquston and transfer aspects, nterface to the control system (fber or copper lnks, data communcaton ndustry standards, etc.).... 7/15 < >

24 Other Aspects Beam couplng mpedance,. e. wake potental of the BPM pckup due to the perturbaton of the beam s EM-feld (adds to the heat load n the cryostat and may cause beam break-up forces n long bunch trans). Assembly and seres producton ssues. Radaton related aspects (cables, connectors, electroncs, etc.) and relablty (MTBF). Costs, number of requred BPM s (TESLA: 2 368). Specal requrements for lnac commssonng, e. g. beam ntensty measurement, lowntense plot bunch orbt observaton (dynamc range!). Data-acquston and transfer aspects, nterface to the control system (fber or copper lnks, data communcaton ndustry standards, etc.).... 7/15 < >

25 Other Aspects Beam couplng mpedance,. e. wake potental of the BPM pckup due to the perturbaton of the beam s EM-feld (adds to the heat load n the cryostat and may cause beam break-up forces n long bunch trans). Assembly and seres producton ssues. Radaton related aspects (cables, connectors, electroncs, etc.) and relablty (MTBF). Costs, number of requred BPM s (TESLA: 2 368). Specal requrements for lnac commssonng, e. g. beam ntensty measurement, lowntense plot bunch orbt observaton (dynamc range!). Data-acquston and transfer aspects, nterface to the control system (fber or copper lnks, data communcaton ndustry standards, etc.).... 7/15 < >

26 CANDIDATES FOR COLD BPM PICKUP S Broadband BPM s (-) Electrostatc Button BPM or electromagnetc Strplne BPM. Broadband transfer characterstc (BW > 1 octave). Pckup electrodes couple to a part of the EM-feld of the beam (mage current), Z elec (x, y) > 0, whch sets the poston senstvty n the order of V A /V B 1 db/mm (assumng 70 mm beam ppe dameter). The BPM resoluton s defned manly by the S/N-rato of the read-out electroncs and t s ntegraton tme. Button pckup based BPM systems have a rather low or moderate snglebunch poston resoluton ( 50 µm). Hgh resoluton (1 µm) s only possble by ncreasng the ntegraton tme (narrow bandwdth, as done n BPM systems of synchrotron lght sources) or usng long strplne pckups n a small beam ppe aperture (SLAC FFTB). Low-cost, smple mechancs (Button BPM s), and low wake potental. 8/15 < >

27 Sem-Resonant BPM s (+) Re-entrant coaxal-cavty BPM. Broadband transfer characterstc (BW > 100 MHz). 50 Ω loaded transmsson-lne, operated on the beam-excted evanescent felds of the fundamental TE 11 wavegude dpole mode (. e. below cut-off frequency). Expect moderate to good sngle-bunch resoluton ( 10 µm) dependng on ntegraton tme and performance of the read-out electroncs. Good lnearty (< 1 %), moderate operaton frequency. Rather compact dmensons and smple machnable mechancs. Low wake potental. Operatonal experence under cryogenc & cleanroom condtons at a test nstallaton n TTF2(!). 9/15 < >

28 Re-entrant coaxal-cavty BPM for TTF2. 10/15 < >

29 Resonant BPM s (+) Dpole-mode (TM 110 ) pll-box cavty BPM, wth of wthout modfcatons (shape modfcatons to fx the polarzaton axes, wavegude ports to suppress the fundamental monopole TM 010 mode, etc). Narrowband, resonant transfer characterstc (Q ). The beam excted dpole egenmode of the cavty BPM has a lnear beam dsplacement dependence, gvng a zero output sgnal wth the beam n the center. Cavty BPM s have the potental to acheve very hgh resolutons (nm-range), dependng on the TM 110 mode operatng frequency, t s Q-value, and some other factors (precson of the mechancs, common mode suppresson, read-out electroncs, etc.). Cavty BPM s have several ssues, whch can be addressed by modfyng the basc pll-box desgn: xy-axes cross-talk (polarzaton), common mode suppresson, sngle-bunch tme resoluton, wake potental. Long term operatonal experence(!) under cryogenc & cleanroom condtons wth several 1.5 GHz dpole-mode cavty BPM s at TTF. 11/15 < >

30 sgnal level f 010 f 110 frequency Prncple of a cavty BPM. 12/15 < >

1.5GHz cavty BPM of the TTF at DESY, now operatng n

31 1.5GHz cavty BPM of the TTF at DESY, now operatng n the cryostat (up, left). Fgure 6: The BPM Modfed as mounted 1.5 GHzncavty the beam BPM tested lne ofat the EL the ELBE lnac (up, rght). Steerer Examples of cavty BPM s: BPM hor. C-Band cavty BPM tested at the SLAC Σ FFTB, showng 25 nm resoluton! (down, left). 13/15 α < >

Fgure 2: Prototype of the 1.5 GHz-montor. Fgure 9: 5.

of COM free cavty BPM s: on the homodyne prncple. The sgnals comng from the 1.

Ths sgnal comes from an addtonal smaller cavty (reference cavty) operatng at the common mode.

5 The GHzdpole cavtymode BPMresonance tested atwas the5.555 ELBEGHz.

C-Band (4.8 GHz) cavty BPM prototype, below -70 dbm level (fg. 10).

32 Fgure 2: Prototype of the 1.5 GHz-montor. Fgure 9: 5.5 GHz-prototype nstalled nto the test beamlne The read-out electronc for the BPM (fg. 3) s based Examples of ELBE. of COM free cavty BPM s: on the homodyne prncple. The sgnals comng from the 1.5 GHz cavty BPM prototype, TUmontor are down-converted usng a sgnal wth the fre-durnquency equal to the dpole mode frequency of the BPM. scanned n order to fnd common mode and dpole mode the frst measurement the montor sgnals were Berln & DESY (up, left). Ths sgnal comes from an addtonal smaller cavty (reference cavty) operatng at the common mode. FltersNo at common photonjector mode resonance (up, rght). was found and s therefore resonances. 5.5 The GHzdpole cavtymode BPMresonance tested atwas the5.555 ELBEGHz. the front-end of the electroncs select the dpole mode frequency and reduce the nose. The down-converson s car- -80 dbm. C-Band (4.8 GHz) cavty BPM prototype, below -70 dbm level (fg. 10). The expected value s about red out by an I/Q-mxer (n-phase/quadrature), that pro-unfortunatelvdes a phase ndependent measurement and allows for ty the was too weak to be used n the BPM electroncs, al- Sprng-8 the (down, sgnalleft). delvered by the reference cav- determnaton of the offset drecton. The down-converted though t was amplfed. An external oscllator was taken sgnals are amplfed and delvered to the analog-to-dgtal converters. 14/15 The reference cavty s also used for the charge < >

33 CONCLUSIONS Dedcated BPM s and HOM-based beam measurements wll be used for beam poston measurements along the man lnacs. Poston resoluton s an mportant BPM parameter, but many other aspects have to be consdered. The BPM requrements, n connecton to the man lnac beam parameters, have to be worked out and contnuously updated. (Sem)-Resonant BPM s, e. g. cavty BPM, are a good choce as man lnac BPM. 15/15 < >

Filling level and Temperature Sensor HFT C4 / R / MD

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