1. BPS Location in CTF3/CLEX Area Mechanics with PCB Electronics Test Results BPS Linearity Error A linear fit of the wire test measures was done (left) for vertical and horizontal plane: Δ[V,H]/Σ vs X [V,H]. The relevant parameters are the slopes that defines the BPS sensitivity: S V =(41.09±0.08)10 −3 mm -1, S H =(41.53±0.17)10 −3 mm -1 ; and the electrical offset from the mechanical center, obtained for Δ[V,H]/Σ= 0 in the linear fit: EOS V =(0.03±0.01)mm, EOS H =(0.15±0.02)mm. The linearity error was obtained for several positions in the range of interest ±5mm (right), getting rms linearity error for each plane, σ V = 80μm and σ H = 170μm giving the uncertainty in the position measurements and so the precision at low current. BPS Frequency Response f LΔ and f LΣ must be lower than 10kHz to avoid flat-top droops in the sensed beam pulse with τ pulse =140ns, getting τ droopΔ, τ droopΣ ~ 10 2 τ pulse ; like in the scope picture for ΔV=V + –V-. Low cut-off frequencies for Δ and Σ: f LΔ = f LΔV = f LΔH = 282kHz ↔ τ droopΔ = 1/ω LΔ = 564ns < 10 2 τ pulse f LΣ = 1.76kHz ↔ τ droopΣ = 1/ω LΣ = 90.4μs > 10 2 τ pulse Δ droop is compensated, or f LΔ lowered, by RC filters in the external amplifier.Also to avoid pulse overshooting distortions, Δ and Σ high cut-off frequencies could be determined over 100MHz despite of HF reflections due to long wire setup. Abstract A prototype of Beam Position Monitor (BPM) for the Test Beam Line (TBL) of the 3rd CLIC Test Facility (CTF3) at CERN has been designed and constructed at IFIC in collaboration with the CERN CTF3 team. The design is a scaled version of the BPMs of the CTF3 linac. The design goals are a resolution of 5μm, a overall precision of 50μm, in a circular vacuum chamber of 24 mm, in a frequency bandwidth between 10kHz and 100MHz.The BPM is an inductive type BPM. Beam positions are derived from the image current created by a high frequency electron bunch beam into four electrodes surrounding the vacuum chamber. In this paper we describe the mechanical design and construction, the description of the associated electronics together with the first calibration measurements performed in a wire test bench at CERN. Conclusions and Future Tasks A set of two prototypes with the associated electronics were designed and constructed. The electric model and characterization parameters as sensitivity, linearity, electrical off-set and cut-off frequencies has been determined with a wire method test. The performed test yields good linearity results and reasonably low electrical offset from the mechanical center. A new improved setup will be built for testing the BPS’s series. Prototype calibration with beam in CTF3 will be performed this coming fall. Half PCB (with 2 sensing transformers) Wall Current through Electrodes Toroidal Transformer [with secondary winding] Output conductors Calibration Input conductor Transformer-electrodes [screwed into wall-el-ectrodes] BPS Low Frequency Model Output signals from the electrodes secondary: where I elec increases when the beam aproaches to its electrode, and N=30 is the number of turns in the transformers secondary winding. Difference signals: and Sum signal: yielded by external amplifier. I B is the total beam current that equals to the sensed wall image current. Designed transresistance is Σ/I B = 0.55Ω. Δ[V,H] and Σ low cut-off frequencies: where L Δ is the electrodes inductances L Σ is the ferrite-body inductance; R C is the electrodes parasitic resistances and R P is the input resistance seen from the transformer primary: R P = (R S1 ||(R S2 +R Load ))/N 2. References S. Doebert, D. Schulte, I. Syratchev, “Status report of the CTF3 Test Beam Line”, CTF3 Note 076. M. Gasior, “An inductive pick-up for beam position and current measurement”, CERN-AB-2003-053-BDI. I. Podadera, S. Calatroni, L. Søby, “Precision Beam Position Monitor for EUROTeV”, EUROTEV Report 2007-046.