1. Tesla Meeting Frascati 27/05/03 C. Magne Cold BPM for TTF2 Tesla prototype - low beam impedance - cooling to 2K without strain - Low beam coupling impedance: reduces the beam break-up forces and minimizes the cryogenic heat-load due to resonances. - The (axial) geometry is favorable to cooling to 2K without strain. - The dimensions are small. - The design is adapted to UHV dust- free conditions. - The mechanics is relatively simple to machine (lathe  precision of axial sym.) Ability to measure sum signal and dark current

2. Tesla Meeting Frascati 27/05/03 C. Magne WIDE-BAND MEASUREMENT Antennae mechanically and electrically connected to opposite wall of the cavity very low external Q 1 : antennae fully pushed ~100 MHz bandwidth 2 : antennae withdrawn Then the BPM bandwidth is determined by the Bessel filter downstream : filter mono dipole on TTF: 4 or 8 MHz

3. Tesla Meeting Frascati 27/05/03 C. Magne  78 beam pipe 8 mm gap 50 mm cavity length 140 mm total length with flanges 650 MHz demountable Severe tolerances were applied on R1, R2, and the perpendicularity of the assembling surface (2/100). Concentricity actually measured : better than 20  m. When cooling down to 2K: - the cylindrical shape of the cavity, and the outer position of the antennae, are perfectly preserved - the room t° calibration is still valid (out of resonance measurement). TTF1

4. Tesla Meeting Frascati 27/05/03 C. Magne RESULTS ON TTF1 5 reentrant BPM installed on BPM, one at 2K inside the capture cavity cryostat. 1COL1 : BW = 8 MW measurement range : +/- 3 mm detected signal: FWHM = 130 ns 1: Delta signal 2: Sum signal From noise (15 mV) and sensitivity (1.5 V/mm) levels: estimated resolution @ 0.8 nC = 10 µm Extrapolations (caution !) : - resolution ~ beam charge - resolution ~ sqrt ( BW ) Only valid if isolation S/D < 50 dB over whole bandwidth

5. Tesla Meeting Frascati 27/05/03 C. Magne 22/01/02 Reentrant BPM for TTF2 Fabrication and mounting procedure Reentrant BPM for TTF2 Fabrication and mounting procedure Fabrication of the BPM cavity The 2 parts of the cavity are assembled by EB welding Leak test Fabrication of the feedthroughs. At Saclay Fabrication of the part: flange with bellow. (Shorten the bellow) Firing of the flange+bellowAt DESY Cu coating of the flange+bellow Firing (900  C) of the BPM cavity Welding of the flange+bellow to the BPM cavity.At DESY RF calibration.At Saclay Welding to quadrupole beam tube, (TIG welding from inside, with tool providing centering and azimuthal positioning). At DESY Cleaning of the BPM cavity. Cleaning of the feedthroughs.At DESY Mounting onto quadrupole, (Centering of the BPM w.r.t. the quad is made with an external part, which is fixed by a few TIG welding points)At DESY

6. Tesla Meeting Frascati 27/05/03 C. Magne - Firing 1200°C Cu coated bellow (Fluhman) RF calibration on testbench (rod simulates beam) Chemistry TIG welded (from inside) to quad beam pipe Will be installed in ACC1 Cold bpm for ttf2 - status X (mm) Y (mm) RF calibration - mapping

7. Tesla Meeting Frascati 27/05/03 C. Magne CALIBRATION 50   HP8510A Network analyser

8. Tesla Meeting Frascati 27/05/03 C. Magne HP8510A Network analyser 50  CHECK AFTER MOUNTING rlu l -24.3 dB -41.6°deg. u -17.01 -25.6° -16.95 -23.3° d -17.07 -25.5° -17.07 -24° -24.33 -42°

9. Tesla Meeting Frascati 27/05/03 C. Magne PROPOSED PARAMETERS FOR A BPM @ TESLA to be discussed The ratio (meas. range)/resolution cannot exceed a few 10 2. To be studied: - isolation of the hybrid coupler - digitized processing after frequency downconversion to 200 MHz. measurement frequency900 MHz Bessel filter bandwidth50 MHz detected signal FWHM20 ns position resolution @ 4nC/bunch1 µm time resolution20 ns working at 2K

10. Tesla Meeting Frascati 27/05/03 C. Magne “R and D on rf-cavity BPM inside a cryomodule” in the SRFTECH Joint Research Activity. (SRFTECH, Superconducting Radio-frequency Technology, Co-ordinator : T. Garvey ) testing of one such BPM in a TTF2 module, and possibly the design of a new electronics. Milestones: Mid-2004 (As soon as TTF2 commisionning with beam is started): results of the prototype installed in the cold module: performance with analog electronics and cryogenic losses. Beg-2006 Commissionning of BPM with new digital electronics. If approved this program will start beg. of 2004.

11. Tesla Meeting Frascati 27/05/03 C. Magne Possible program for a new R & D An improvement in the resolution, flexibility and cost of the BPM is needed to meet the TESLA requirements. The goals for the new R & D are: - To increase the resolution to 10 µm while keeping a fast time response. This will will be obtained by 2 improvements: - optimization of the rf cavity shape to have a better common mode rejection, - design and fabrication of a high isolation hybrid coupler. The parameters required for TESLA are a 10 µm resolution and a time response as low as possible. - To adapt the cavity mechanics to the adjacent new superconducting quadrupole developed by CIEMAT/DFFPE, Madrid. The alignment tolerance is 100 µm. - To provide a more flexible operation. This will be obtained with the design and fabrication of a new electronics based on digital signal processing. It will benefit from the low cost components developed by the telecommunication industry. outlook BPM based on a cylindrical reentrant RF cavity equipped with 4 weakly coupled antennae. The associated wideband electronics allows 100 ns time-domain response without too much degradation of the resolution (in the case of the very short TESLA bunches).

12. Tesla Meeting Frascati 27/05/03 C. Magne Transparency D. Nölle

13. Tesla Meeting Frascati 27/05/03 C. Magne Dark Current Monitor - design Optimised to measure the monopole mode signal at 1.3GHz. However we keep the 4-antenna design for 2 reasons: - the sensitivity and homogeneity of the dark current measurement is increased - it can be used as a BPM later, by adding adequate electronics. Dipole mode frequency = 2.6 GHz. antenna

14. Tesla Meeting Frascati 27/05/03 C. Magne Dark Current Monitor – laboratory test F mono = 1.3 GHz F dip = 2.6 GHz Alu prototype An aluminium prototype has been fabricated to study the optimum antenna design. - Network analyser - testbench Electronics (analog): - One unit (refurbished) is avalaible - Need to build 1 (or 2?) more