TOPSHIM Automatic Shimming Precautions 

Automatic Shimming with a Solvent Height of 4 cm:

Topshim is a programmed feature for automatic shimming in nuclear magnetic resonance (NMR) instruments. Optimal performance is achieved when using a solvent height of 4.0 cm (650 μl). The use of automatic shimming (Topshim) is prohibited when the sample solvent is shorter (< 3.0 cm).

When the solvent is less than 3 cm in height, Topshim will utilize higher current in the higher-order shimming coils to complete the shimming task. This results in an increase in the temperature of the shimming coil, causing a drastic change in the magnetic field. This temperature rise can ultimately lead to the gradual loss of functionality of Topshim.

Improvement Methods for Insufficient Solvent Height: (Choose one of the following)

1. Increase the solvent volume to achieve a height of 3 - 4 cm (requires 500 μl - 650 μl).

2. Use a Shigemi tube with a height of approximately 2.0 cm (requires 330 μl).

3. Manual shimming: Use the mouse wheel to adjust z1, z2, x, y, and other second-order shim keys in the bsmsdisp Main window. Ensure that the lock level in the lock window continually rises until it cannot go any higher.

Explanation: Manual shimming does not affect higher-order coils dramatically and avoids disturbances in the    

                        magnetic field current.

Reminders:

1. When the solvent is insufficient, ensure that the sample centerline is aligned with the probe centerline.

2. Before starting shimming, pre-load the ShimFile (rsh bbfo).

3. Prior to closing Topspin, each user must reload the ShimFile (rsh bbfo) to ensure that the current returns to normal values before exiting.

TOPSHIM 自動勻場注意事項 

溶劑高度 4 cm 高的自動勻場：

Topshim 是核磁共振儀自動勻場之程式設計，自動勻場在使用 4.0 cm 高 (650 ul) 溶劑有最佳果效，如果樣品溶劑較短 (< 3.0 cm)，禁止使用自動勻場 (topshim)。

當溶劑較少(如 3 cm 高)時，Topshim 會在高次方勻場線圈使用更大的電流來完成勻場任務，而使勻場線圈的溫度 (Shim Coil Temperature) 增加，升高的溫度會導致磁場變化激劇，最後使 Topshim 漸漸失能。

溶劑高度不足改進之法：(須擇一而行)

1. 加足溶劑直到 3 ~ 4 cm 高 (需 500 ul ~ 650 ul)

2. 使用 shigemi tube 約 2.0 cm 高(需 330 ul)

3. 手動勻場：使用滑鼠滾輪在 bsmsdisp Main 頁中勻 z1, z2, x, y

    及其他 2 次方以下 shim key，並使 lock level 在 lock window

    視窗中不斷上升至不能而已。

說明：手動勻場不勻高次方線圈，不激劇影響磁場電流

提醒：

1. 溶劑不足時，樣品中心線應置於量深器中心線處

2. 勻場開始之前，預先讀入 ShimFile (rsh bbfo)

3. 每位使用者關閉 Topspin 之前，務必再讀入 ShimFile (rsh bbfo) 以確保電流回歸至正常值才離開