Monitoring

Burn-off efficiency

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A common figure of merit used to quantify the condition of the LHC is the lifetime of the beam. It provides important information for the LHC as a storage ring, but does not inform about the luminosity production of the collider. Instead, it is more appropriate to define the instantaneous burn-off efficiency $\eta$, following:

$$\eta \equiv \left[\frac{dN}{dt}\right]_\text{bo}\bigg/ \left[\frac{dN}{dt}\right]_\text{total} = \frac{\sigma_\text{pp} \mathcal{L}}{\sigma_\text{pp} \mathcal{L} + R_\ell N}$$

where $\left[\tfrac{dN}{dt}\right]_\text{total}$ and $\left[\tfrac{dN}{dt}\right]_\text{bo}$ are the total and burn-off losses, $N$ is the beam intensity, $\mathcal{L} = \sum_{\text{IPs}}\mathcal{L}_\text{IP}$ is the total luminosity of the collider, $R_\ell$ is the loss rate from non-burn-off losses and $\sigma_\text{pp} = 80\ \text{mb}$ is the accepted value for the cross section of proton-proton collisions at 7 TeV. The efficiency is similar to the effective cross section $\sigma_\text{eff}= \frac{1}{\mathcal{L}}\left[\sigma_\text{pp} \mathcal{L} + R_\ell N\right]$ used in previous work. One can note that $\eta = \sigma_\text{pp}/\sigma_\text{eff}$. To optimise luminosity production, a well-behaved machine needs to lose most of its protons to collisions, i.e. $\eta \to 1$. Assuming small $R_\ell$ over a short period of time compared to the length, $T$, of luminosity production for a fill, one can show that the relative gain in integrated luminosity, $G$, scales with the integral of $\eta(t)$, or more precisely: $$ G \sim -r_0\left[\frac{r_0 T + 2}{r_0 T + 1}\right] \cdot \int_0^T\left(\frac{1}{\eta} - 1\right) dt $$

where $r_0 = \sigma_\text{pp} \mathcal{L}_0/N_0$ is a constant which depends on the initial conditions (with units of \unit{s^{-1}}). Alternatively, one can see that $\left(\frac{1}{\eta} - 1\right) = \frac{R_\ell N}{\sigma_\text{pp} \mathcal{L}}$ corresponds to the luminosity-normalized losses of the machine. For example, if $\eta = 0.5$ for 30 minutes in typical LHC conditions ($N_0 = 2400\cdot 1.3\times 10^{11}\ \text{p}^+$ and $\mathcal{L}_0 = 2\times (2.2\times10^{34}\ \text{Hz/cm}^2)$), the change in integrated luminosity is $G \sim -3\ \%$ for $T=10\ \text{h}$. Hence, the experimental efficiency is to be discussed on the basis of its deviation from $\eta=1$ over a certain period of time.

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Special fills

Fill	Comments	Efficiency	B-by-B signature
8348	MD8043, Nov 2022	DBLM | BCTF	DBLM | BCTF
8462	MD7003, Nov 2022	DBLM | BCTF	DBLM | BCTF
8469	MD7003, Nov 2022	DBLM | BCTF	DBLM | BCTF
8470	MD7003, Nov 2022	DBLM | BCTF	DBLM | BCTF

Fill-by-fill monitoring

Extra fill-by-fill summary data can be found on the BPT Dashboard

Fill	Wires status	$\beta^*$	Bunches B1/B2	Efficiency	B-by-B signature
8685	OFF	30.0 cm	411/411	DBLM | BCTF	DBLM | BCTF
8686	ON	30.0 cm	399/399	DBLM | BCTF	DBLM | BCTF
8690	ON	30.0 cm	399/399	DBLM | BCTF	DBLM | BCTF
8695	ON	30.0 cm	911/911	DBLM | BCTF	DBLM | BCTF
8696	ON	30.0 cm	999/999	DBLM | BCTF	DBLM | BCTF
8701	ON	30.0 cm	999/999	DBLM | BCTF	DBLM | BCTF
8723	ON	30.0 cm	399/399	DBLM | BCTF	DBLM | BCTF
8725	ON	30.0 cm	999/999	DBLM | BCTF	DBLM | BCTF
8729	ON	30.0 cm	1163/1163	DBLM | BCTF	DBLM | BCTF
8730	ON	30.0 cm	1163/1163	DBLM | BCTF	DBLM | BCTF
8731	OFF	30.0 cm	1818/1818	DBLM | BCTF	DBLM | BCTF
8736	ON	30.0 cm	1818/1818	DBLM | BCTF	DBLM | BCTF
8738	ON	30.0 cm	1818/1818	DBLM | BCTF	DBLM | BCTF
8739	ON	30.0 cm	1818/1818	DBLM | BCTF	DBLM | BCTF
8741	OFF	30.0 cm	1903/1903	DBLM | BCTF	DBLM | BCTF
8746	ON	30.0 cm	2374/2374	DBLM | BCTF	DBLM | BCTF
8754	ON	30.0 cm	2374/2374	DBLM | BCTF	DBLM | BCTF
8771	ON	30.0 cm	2374/2374	DBLM | BCTF	DBLM | BCTF
8773	ON	30.0 cm	2374/2374	DBLM | BCTF	DBLM | BCTF
8775	ON	30.0 cm	2374/2374	DBLM | BCTF	DBLM | BCTF
8786	ON	30.0 cm	2374/2374	DBLM | BCTF	DBLM | BCTF
8804	OFF	30.0 cm	2374/2374	DBLM | BCTF	DBLM | BCTF
8822	ON	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8850	OFF	30.0 cm	705/705	DBLM | BCTF	DBLM | BCTF
8853	OFF	30.0 cm	1195/1195	DBLM | BCTF	DBLM | BCTF
8858	OFF	30.0 cm	1650/1650	DBLM | BCTF	DBLM | BCTF
8860	ON	30.0 cm	1886/1886	DBLM | BCTF	DBLM | BCTF
8863	OFF	30.0 cm	1650/1650	DBLM | BCTF	DBLM | BCTF
8865	ON	30.0 cm	1650/1650	DBLM | BCTF	DBLM | BCTF
8870	OFF	30.0 cm	1886/1886	DBLM | BCTF	DBLM | BCTF
8873	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8877	ON	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8880	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8882	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8885	ON	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8887	ON	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8891	ON	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8894	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8895	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8896	ON	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
8901	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
9017	OFF	30.0 cm	399/399	DBLM | BCTF	DBLM | BCTF
9019	OFF	30.0 cm	911/911	DBLM | BCTF	DBLM | BCTF
9022	OFF	30.0 cm	1178/1178	DBLM | BCTF	DBLM | BCTF
9023	OFF	30.0 cm	1886/1886	DBLM | BCTF	DBLM | BCTF
9029	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
9031	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
9035	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9036	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9043	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9044	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9045	OFF	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9046	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9049	OFF	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9050	OFF	30.0 cm	2358/2358	DBLM | BCTF	DBLM | BCTF
9057	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9063	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9070	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF
9072	ON	30.0 cm	2464/2464	DBLM | BCTF	DBLM | BCTF